By box I assume you mean square face.
Draw your 1" spaced guide-lines over the face [on it] - as a grid.
Now draw your Lines on the face, so those new lines snap onto the face.
Use the guide-grid to help - BUT you can just draw and set exact lengths by typing and pressing enter…
or use snaps/inferences etc…
I think you are missing the very basic fundamentals of Sketchup.
It is easiest to work with faces to align edges. Also you need to understand the basic concept of ‘Start an action with a click, then take your hand off the mouse and type what you need then hit Enter to finish the action.’
As you see here, I create 8 by 8 face, then a 1 by 1 square on that face, then mid point inference…
I think I got the hang of it. I am now trying to create a spade.
3d box.skp (78.3 KB)
Now I need to work on how to flip this design
3d box.skp (79.4 KB)
I am unable to get my image on the green line which I think is causing my flip to not work.
Select the edges that need to move and use the Move tool. It would have been easier if you’d just drawn it in the right place to start with.
Flip:
Erase the unwanted faces first…
If you want to make a flipped copy - ‘around’ the green axis, then you need to choose flip ‘along’ the red axis !
Make a copy of what you want to flip off to the side and flip that.
Then you can select it and move it back, snapping onto the original part.
I also note that your Model Info > Units is set to snap to 1"
Uncheck that option - it’s probably causing you some issues when drawing things only ~1" !
I think I got it but now when I try to pull it to 1" I get negative and when I do type in 1" it’s not working correctly.3d box.skp (93.9 KB)