How to Model Close-Fitting Parts with SketchUp’s Trim

By Aidan Chopra

Woodworkers and industrial designers, take heed: SketchUp Pro’s Trim tool saves you literally hours of work. Anytime you need to build a model with parts that interlock or otherwise fit together closely, Trim is where you should look first.

Trim basically tells one part to “take a bite” out of another, which is perfect for joinery (dovetails, finger joints, dadoes, and so on), machine parts, ball-and-socket joints, and any other positive/negative conditions where two parts meet.

The figure shows a small wooden box with dovetailed sides and a dadoed bottom.

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The only tricky thing about using the Trim tool is remembering which solid to pick first. Remember that the first thing you pick (or click) is the one you want to use to cut with. In the case of the box in the figure, that would be the side with the dovetails.

When you select the dovetails and then select the blank side, the Trim tool cuts the dovetails into the second piece. You get the hang of it after a few tries.

The Trim tool has a neat trick up its sleeve: You can keep using your cutting solid on multiple other solids. To cut the dado (or groove) into the sides of the box, follow these steps:

  1. Choose Tools→Solid Tools→Trim to activate the Trim tool.

    Your cursor has the number 1 on it.

  2. Select the box bottom.

    Your cursor changes to show the number 2.

  3. Select one side on the box.

    You just cut a dado using the box bottom you picked in Step 2. Your cursor still says 2.

  4. Select another of the box’s sides to create another dado.

  5. Select the remaining two sides to cut dadoes in them, too.

A question that comes up pretty frequently concerning what happens when you use one of the Solid Tools on a component instance. Why doesn’t the effect of what you just did affect all the other instances of that component? It should, shouldn’t it?

Here’s the thing: As soon as you use a Solid Tool on a component instance, SketchUp makes that instance unique; it’s still a component — it just isn’t connected to the other instances anymore.