Trim, extend and split

When you draw shapes that overlap, some pieces of line get in the way. Trim removes them, so you are left with one clean outline. For example, draw a circle overlapping the top of a rectangle, then trim the pieces in the middle to get a bookend with a round top. Extend does the opposite: it stretches a line until it meets the next line, arc or circle.

Trim#

1. In a sketch, click Trim, or press X.
2. Click the piece of line, arc, circle or ellipse you want to remove. The piece between the nearest crossings on either side of your click goes.
3. Keep clicking pieces. Press Esc when you have finished.
4. A line that crosses nothing is deleted completely.
5. A circle must cross other lines in at least two places to be trimmed. Otherwise it is deleted.
6. A trimmed ellipse becomes an elliptical arc. Trim it again to shorten it or split it.
7. The new ends stay joined to the lines they were cut at.
8. Crossings with construction (dashed) lines do not count.

Extend#

1. Choose Extend from the ▾ next to Trim.
2. Click near the end of the line you want to stretch.
3. The line grows until it meets the next line, arc, circle or ellipse in that direction, and stays joined to it.

Only a loose end can be extended, not an end joined to another line. If the line has a length dimension, it changes to the new length.

Split#

Split breaks a line or an arc in two where you click, like Split in Onshape and Split Entities in SOLIDWORKS: for example, to give one side of a shape a notch, or to dimension part of a line.

1. Choose Split from the ▾ next to Trim.
2. Click the line or arc where it should break.

The two pieces share a new point. A line's pieces stay in line (and horizontal or vertical if it was); its length dimension goes, so dimension the pieces instead. An arc's pieces keep its centre and radius. A circle has no ends, so it cannot be split: trim it, or draw two arcs.

Step by step#

Here is the whole thing on a bookend with a round top, from the SchoolCAD video tutorial.

over the top edge of a rectangle.](trim-step-1.webp)

it.](trim-step-4.webp)

Tips#

• You do not always need to trim. Lines that cross split a sketch into separate shapes, and Extrude lets you choose which of them to use. Trim when you want one clean outline.
• Trim works on lines, arcs, circles, ellipses and elliptical arcs, not on splines.
• Trimmed the wrong piece? Press Ctrl+Z.

If it does not work#

• Click on the piece of line, circle or ellipse to remove. You clicked empty space, a point or a spline.
• Click near the end of a line to stretch it. Extend only works on lines.
• There is nothing for this line to meet that way. Nothing crosses the path of the line in that direction.
• That end is joined to another line. Extend a loose end.