Free and Constrained Drawing

Exercise 12 – Let’s Draw

A Line in CAD terminology is straight. It is the shortest distance between two points. If it’s bent then it is a curve, arc, circle or ellipse and not a line. Think of it as being drawn along a straight edge.

Let’s start drawing and explore several ways to draw a straight line. You’ll be surprised to discover how many ways there are. We’ll begin with a new blank drawing file.

  1. Select File, New from the dropdown menu. (Don’t save your currently open drawing).
  2. Select the Insert Line command

  3. Look at the prompt. It tells you what to do, ‘Select the start of the line’


  1. Just click any location on the drawing area to start your first line. Then move your cursor and notice a ‘rubber band’ line and a distance display attached.
  2. Look at the prompt It will be asking the next question, ‘Select the end of the line’.

Place a second point somewhere on the screen and a line is drawn. Woohoo!

The software continues to let you draw lines without reselecting the command.

  1. Place a third point on screen to draw your second line, then continue to place as many lines as you desire. Be sure the end points of each line are not on top of another line.

If you attempt to make your lines vertical or horizontal by eye, you’ll never get it exact, even if it looks perfectly vertical or horizontal on the screen!

  1. When you’re satisfied with the lines you’ve drawn, RIGHT click ONCE to end the process.

Look at the prompt! By right clicking only once you have stepped back only one step in the process, you have not exited the command completely.

  1. Click a new position on the drawing to begin a new line and again continue to place more lines in the drawing space.

You’ll probably end up with a messy looking web of lines weaving their way all over your screen.

  1. Whilst you still have a ‘rubber band’ line attached to your cursor use the mouse wheel to zoom and pan around the drawing. Notice you’re doing this whilst still in the middle of drawing. Cool.
  2. Now press Ctrl + Z (Command⌘ + Z) on the keyboard to undo the last line drawn. Each time you undo, the lines will appear to unstitch whilst leaving you ready to continue inserting more lines.
  3. Play with inserting a few more lines, then when you’re completely finished click the RIGHT mouse button TWICE or press the Esc key to exit the command completely.

Look at the prompt. It should have returned to neutral and say… Select Command or Entities.

Freely place lines are ok but what if we need to be more structured or constrained? Let’s delete the ones we just inserted.

  1. Select all the lines, then press Delete (Fn + Delete) on the keyboard to remove them, or press the garbage bin icon in the Quick menu.

Exercise 13 – Shift Key = Constrained Movement

In most technical or architectural drawings, you’ll need to constrain your lines in much the same way as you would with a T-Square and Set-Square’ on a drawing board.

Here are just a few ways we can do this.

  1. Select the Insert Line command again.

Check the prompt. (Get into the habit of looking at the prompt)

  1. Click a location somewhere on the screen to start your line. Then move your cursor around and again notice a free moving ‘rubber band’ line and a digital distance readout attached.
  2. Now hold down the Shift key on your keyboard, and as you move your cursor around the screen, you’ll notice the movement jumps to a series of pre-set angles.

The ‘factory pre-set’ angle is multiples of 45 degrees and so the cursor movement is constrained to 0, 45, 90, 135, 180, 225, 270, 315, 360 degrees.

  1. Whilst holding the Shift Key, try to draw the following shape.

  2. Release the Shift key and notice the software reverts back to free lines.

Note: The angle of constraint can be set to any useful angle you desire.

  1. Select Options, System from the dropdown menu or the Cog icon from the Quick toolbar.
  2. Set the Auto snap angle to 15 and click OK.
  3. Now try drawing with the Shift Key held down. You’ll notice you have more angle options to choose from, but all of them are a multiple of 15 degrees.

  4. Now set the Auto snap angle to 90.
  5. When you hold the Shift Key now, you’ll only be able to draw horizontal or vertical lines. In some CAD software this is known as ‘Ortho’ mode. Try it out.


The Shift Key operates not only to constrain movement when drawing lines but to constrain the movement of your crosshair when you are performing almost any command such as when dragging an entity around your drawing, just as you did when moving the food to the plate.

Exercise 14 – X and Y Constrained Lines

Using the Shift key to constrain a line to a desired angle is great, but as you found out, the line jumps from one angle to the next depending on the location of your cursor. What if you wanted to force a line to draw horizontally no matter where you clicked on the screen without the need to set Auto Snap angles or hold your shift key? It’s easy…

  1. Select the X-Axis Line Look at the Prompt.

  1. Now insert a whole bunch of lines.

You won’t have to reselect the command each time because the software will keep the command active until you click the right mouse button to say to you’ve finished.

No matter where you move your cursor the lines refuse to budge off the X-axis.

  1. Repeat the above using the Y-Axis Line Notice what happens if you select a horizontal line as the start or end of the vertical line you’re drawing.

Your drawing should look similar to the one above.

Notice that the vertical lines follow the ‘Y’ Axis as indicated on the Workplane.

Let’s save this drawing now so we can use it later.

  1. Select File, Save-As from the icon or dropdown menu

You’ll be presented with a Save-As dialog box asking for a file name and a location to save this file.

  1. Choose a location you and name the file ‘My Training Pattern’ and then select

Remember the folder location on your computer because you’ll need to access your saved files later. Write the location down if you have to.

Trial Mode

You may get a message to ‘buy now’, ‘set license key’ or select ‘trail mode’. Select Trial Mode. You may then get a dialog box as shown here…

This is because you’re using the software in Trial Mode and can only save drawings with less than 100 entities. If you get this message it means you’ve used more than 100 entities so go back to the drawing and delete some of the lines and try to save the drawing again.

  1. Look at the Title Bar. You should be able to see the file name you created on the bar.

Exercise 15 – Grid Constrained Lines

The concept of using a Grid in CAD is pretty much the same as using graph paper when drawing by hand. A grid is there to help you stay aligned. You can also count the spaces when you need to draw at lengths along the grid and your length horizontal and vertical will be in modules of your grid spacing. When you snap to the grid points in CAD it will be 100% accurate.

  1. Select File, Open from the dropdown menu or icon menu

  1. Select the file named ‘Grid-Lock’ from the Training folder. Apart from the rectangle and some numbers in the lower left of the view there is nothing else in this drawing.


  1. Zoom-Fit the drawing to make the most of your work space.
  2. From the Quick Menu toolbar select the Grid icon

  3. Set the dialog options to the values shown above and click OK.


The best way to move from one field to another in any dialog box, in any software, is to press the ‘Tab’ key on your keyboard. It is much quicker than using your mouse. You can also use the Space bar to check and uncheck check boxes! (Also called tick boxes)

The grid should now display. You’ll notice small and large markings. The small markings are the X and Y spaced points and the large markings are the X and Y Reference markings.

  1. Select the Colour from the Style Bar

  2. Choose colour 5 by double clicking on it. Colour 5 now becomes the active
  3. Select the Insert Line command and create the following drawing, checking the values displayed near your cursor as you draw. (Don’t add the actual dimensions to your drawing)

You’ll notice that as you move your cursor horizontally or vertically, the values jump in increments of 100 and when you click near a Grid point the line snaps to the nearest point.

Grids help greatly when you need your designs to be modular. By setting the grid value to the smallest modular value you can be sure the entities you draw either in the X or Y directions will be limited to increments of that value.

The appearance of the grid can be a little annoying at times, especially as you zoom out, so the software will automatically hide the grid display if the dots get too close to each other. The snapping action of the grid is still effective though.

  1. Hold your cursor in the middle of your drawing and zoom out until the grid dots switch off.
  2. Zoom-Fit to bring the drawing back to fill your screen.

You can also switch the Grid to display as lines like those on graph paper.

  1. Open the Grid dialog again and check the Display grid as lines Then OK

The grid should now appear as lines on screen.

You can also customise the colours of these grid lines to suit your personal preferences but we won’t bother with that here. Let’s switch the grid visibility off but leave the snapping action on.

Open the Grid option dialog yet again and uncheck the Display Grid check box only. Click OK

The Grid is no longer visible; however, cursor movements will still be confined to increments of 100.

  1. Without the grid showing, draw the balustrade lines as shown.

Be sure NOT to let your cursor be a diamond shape when you start the angled lines of the hand-rail as this will force them to be perpendicular (at right-angles) to the line you touch. Move your cursor a little further away from entities so the diamond disappears before you click.

Take Control

By holding down Ctrl (Command⌘) the diamond cursor will temporarily be disabled and your new line won’t lock perpendicular, even if you’re right on top of another line.It will still snap to the grid though – Yay!

Part of the learning in this exercise is to get more skilled control over your mouse movement. If you get too close to a line, the system will assume you want to use the line to snap to rather than the Grid point. After a short while you’ll become very dexterous at manipulating your cursor and very aware of what your cursor is indicating to you.

Getting the angle of the railing to follow parallel to the slope of the stairs will be a challenge for some of you! Enjoy working out how to do this. J


You may also have noticed we are now drawing in a different colour. Be sure to select the new blue colour #2 to draw with before you draw;
If you’ve raced ahead before reading this note and have already inserted the lines, simply select those lines and change their colour. You don’t need to redraw them.

  1. Use File, Save-as to create a new CAD file called ‘My Training Steps’

Again, remember the folder you’re saving to. You’ll later be required to submit this drawing for evaluation and marking.

Cool Tips

– Alt + G on the keyboard toggles the Grid display on/off and Alt + S toggles the Grid snapping action on/off.You can use these toggles whilst you’re in the middle of drawing.

-Use the Grid to easily keep all your text, labels and dimensions in alignment as you insert, move or copy them around your drawing.It will help your drawings to be neat and more legible.

-The angle of the grid can be changed by entering a value in the Grid Options dialog or by changing the angle of the WorkPlane.The origin of the grid (the set-out position) can be moved by moving the Workplane.