Thick & Thin lines are used in both 2D and 3D sketching to help communicate design work; to enhance ideas to lift off the page; to help convey vital information. Companies such as Ikea and Lego use Thick & Thin lines in all of their instruction manuals. Designers use Thick & Thin lines to enhance the presentation of their ideas and communicate key areas. It is a simple technique that if applied well enhances your design work however if it is applied wrongly then it can ruin a good sketch!
To apply Thick & Thin lines is relatively simple. The OUTER edge of the sketch is ALWAYS THICK! Lines on the INSIDE are almost always THIN! There are exceptions however.
The image shown has a thick outer edge to the design work. This has been applied with a thicker fine line pen. The lines on the inside are thin lines.Â