Drawing a perfectly straight line freehand is very difficult. The long straight edges of rules can be used as a guide to draw straight lines, as long as the rule is in good condition and the edge is straight. A rule can also be used in this way with a cutting tool, to aid with cutting or scoring straight lines in a material.
Make sure the rule you are using is long enough to cover the distance you need to draw. If you have to reposition the rule rather than making a continuous line, the line might not be completely straight.
The line you draw will probably be slightly displaced from the very edge of the rule. How much will depend on the thickness of the rule, the drawing implement and the position the drawing implement is held in against the edge of the rule.
To get the most accurate line, the drawing implement should have a thin point or nib which is held at a steady angle against the edge of the rule as it draws the line.
If you are drawing with ink, the line can be smudged by the rule touching the surface you’re drawing on. To prevent this, a rule with a bevelled edge can be turned upside down. This means the edge of the rule is raised slightly from the surface, which can make it more difficult to be accurate.
How to draw a single straight line with a rule
Step 1 – Mark where to draw
If the line needs to be in a specific place or a certain distance long you might want to measure and mark where it is going. For example, if you wanted to draw a line for a margin on the left-hand side of a page you would measure the distance you want it to be from the edge of the paper.
To make sure the line is parallel to the paper’s side, you can measure the same distance at the top and bottom of the sheet. Mark these measurements and then draw a line joining these marks. If the marks are measured correctly, the line should be parallel from the edge.
Step 2 – Position rule
Place the rule in the position you want the line to be drawn. Hold the rule in the centre of where the line is going, as this should prevent the rule moving as you draw. Try to keep your fingers away from the edge you’re drawing. If you draw over your finger there will be a finger shaped bump in your line.
Step 3 – Draw line
Ensure the rule is in the correct place, hold it steady with one hand and use it to guide the drawing implement. Make sure the point or nib stays at the same angle against the edge of the rule. If the position changes while drawing the line won’t be straight.
How to draw parallel straight lines with a rule
Rolling rules are specifically designed to easily draw parallel straight lines. The roller in the body of a rolling rule means it can be moved up and down while remaining parallel to its original position. Folding rules can also be folded in such a way that two straight edges are perpendicular to each other. This allows one edge to work as a guide for keeping the other edge parallel to its original position.
Standard rules can also be used to draw parallel lines, although you may need to take a little more care to ensure they are completely parallel to each other. Some rules have a hook or buttress on the end, which can be used to keep the rule in a parallel position to the edge of a surface.
Step 1 – Mark where to draw
To draw lines that are parallel to each other it’s advisable to mark out where the lines will go before you draw them. Use the rule to measure the distance apart you want the lines to go. Mark down one side of the paper, or whatever you’re drawing the lines on to, the position you want each line to start.
To help the lines remain parallel the same distances should be marked on the other side, where the lines will end, with one or two other measured marks being placed where the lines will run through. As long as the measurements are accurate and consistent you’ll be able to use them to correctly position the rule to draw parallel lines.
Step 2 – Position rule
Line the rule up with the measured points and hold the rule in the centre, as this should make the rule less likely to move. Try to keep your fingers away from the edge you’re using as a guide.
Step 3 – Draw line
Hold the rule in place with one hand and use the edge to guide the drawing implement. Keep the nib or point of the drawing implement at the same angle against the edge of the rule as you draw. If the position changes while drawing the line won’t be straight.
Step 4 – Draw other lines
Once the first line has been drawn, move the rule down to the next mark and draw that line. Try to position the rule in the same way in relation to the marks each time, for consistency. So, if you are drawing the first line from the top of the measured marks all lines should be drawn from the top of the marks.
You can check the lines are parallel by measuring their distance apart across the length of the lines.