Trimming Solid Objects

I am fairly new to SketchUp Pro, using it only for fun and hobby. My operating system is Windows 7 and my version of SketchUp Pro is 2020.

I have been trying to trim an object in SketchUp Pro without any luck. I cannot use the Solids Tools because I am advised that one of the objects is not a solid. That being the case I searched the internet and found, ‘ADSU Video 0301: Trimming solid objects (Chapter 3), by Alexander Schreyer’, and this appeared to do what I wanted done.

However, when it came to deleting the material on the object, it just left a mess. What am I doing wrong, or how can I accomplish what I am trying to do?


Hard to say from just a screenshot. Can you share your model skp file here and describe more fully the steps you took?

Edit: I see you just joined the forum. You may need to make a few more posts before the forum will let you upload a file.

If you extrude the cutting face into a block with Push/Pull and make it a group, and assuming that the hand rail is a solid group or component, the Solid Tools should work for you.

Upload the file if you can for specific help. Here is some info on using intersect to trim.


Thank you for the information. I will think of a few simple questions to ask.




As I mentioned, I cannot use the Solids Tools because I am advised that one of the objects is not a solid.

I will try to upload my file with this posting.

Staircase - Handrail.skp (2.3 MB)

Very clearly in your screen shot the face you’ve drawn for the cut can’t be solid. A solid must be 3D.

The rail is not a solid group either.

The railing geometry also has other issues due to the way it was modeled.

I also notice you are using layers incorrectly. Layer 0 (Untagged in SU2020) should ALWAYS be the active one and all edges and faces should remain untagged. The pencil icon should always be set to Layer 0/Untagged.

After fixing the rail to make it show as a solid and making the rectangle 3D and a solid group, Subtract does exactly what you need.


Originally the intersecting surface was a solid, but as both objects had to be solid I tried the method proposed by Alexander Schreyer, but could not advance beyond the current state of the drawing.

Also, why should the pencil icon always be set to Layer 0/Untagged? If I do that all of my layers are all shown under Tag 0, which is very confusing when I try to operate on them at a later date.

What I normally do is import an AutoCAD drawing and then write over it using the pencil tool. If I only use Tag 0, how do I separate the two drawings?

As I said, I am a newbie here I don’t know why things are done in a certain manner, but I am willing to learn.


Probably wise to start with the basics, grab a couple of starter tutorials from the SU site. If you don’t get simple concepts down at the beginning, you will be encountering ever more disruptive problems in the future.

Use groups and components to separate the drawings. If you are tracing over an imported drawing. Keep that drawing grouped. You keep Tag0 selected so that edges and faces are all given Tag0. That way you always know where the geometry is. Later you can assign groups and components to other Tags so you can hide/show them by tag. Tags won’t separate your drawings, groups and components will.

I’m sure @DaveR will chime in soon with a more detailed explanation of why there is almost never a reason to change the active tag/layer and to do so is to invite disaster. I’ll give you the quick basic version.

Tags (used to be Layers) only control visibility, they do nothing to physically separate geometry within SketchUp. That job is accomplished using groups and components It is a basic concept of Sketchup that all raw geometry is “sticky” and can interact with all other geometry. So, if you make a line of raw geometry and put it on some tag, even if you turn that Tag off it can still interact with, distort, cut, destroy other geometry that occupies the same space, even while invisible. People often get distorted confusing models that are falling apart because invisible geometry is merging and distorting geometry that they can see. So it is best practice to only place already “sealed” containers of groups and components on separate tags, and to leave all raw geometry untagged where it’s relationship can be seen and carefully managed.

You can make a group of your tracing lines and give that a separate tag, then open the group to trace more or edit, no prob.

Thank you all, I am beginning to understand the problem. I have just watched, ‘SketchUp Training Series_ Layers’, which was quite clear. I have also watched several other SketchUp Training Series videos so eventually I will become more knowledgeable.

I will delete the current problem and attack it in a different way.

Thank you for your help and suggestions.