I haven’t used Sketchup Make for very long but one thing I’ve really struggled with is making precision intersections. For example, if I have a 4" x 4" box, what’s the best way to precisely cut off 2"? (I.e. - cut 50% of it off, cut it in half, etc.)
?
Do I have to just eye it? Because every time I try that, I always wind up having problems with the final cuts…
The question suggests you haven’t got a handle on how to use text input.
If it is raw geometry you can simply copy the bottom up 2".
Select the bottom, then use the move tool with ctrl to make a copy, type 2" and hit enter and you will have a face dead center.
Your response helped me visualize the problem in different perspectives. Instead of using additional shapes to perform intersections with, I instead plotted the boundaries of my “cut” and instead used the rectangle tool to define areas I could “shrink away.” For example, making a 2" x 2" rectangle face and using that to reduce the area into the original shape. (Grouping the entire shape afterwards.)
You could just push it down 2".
See this video tutorial.
Accuracy by Aidan Chopra
Right–that’s basically what I did with mine. 
(That’s what I kind of meant by “shrink away.” Ha.)
The OP only used 4" and 2" as an example. The main goal was to reduce a box to half its height (or length or width).
The way I would do this is by using a temporary construction line and Push/Pull, like this:
You certainly should NOT be eyeing it. That would be what you are doing when you are just sketching something and this software is called…no, hold on…
It’s really interesting seeing how you guys do these things and think about the situations… It’s a new way of thinking about modifying shapes or moving blocks around, etc. I think it’s going to take me some getting used to.
If you want half, just use the midpoint inference.
There are always multiple ways of doing anything.
I always like when a program gives you a choice of more than one way to accomplish something.
Halfway up a 4’ cube is actually an easy special case that the above examples show you how to avoid the obvious use of a plane to cut the object. Lets take an arbitrary shaped object and section it 2/3rds of the way up.
