I want to cut uncessary part of object

i tried to cut this object such like following image
but i couldn’t .
yesterday another people helped me but i followed exact but couldn’t make success.
i upload skp file anyone pls help me.
ps: mesh design some different because i changed mesh


ob.skp (100.7 KB)

ob (SU 2017).skp (222.2 KB)

hi thanks for your help!
how could you make 3d mesh object to 2d ?
you using plugin or other method exist?
sorry i too much novice for sketchup

I redrawed it from scratch just by 2D, using rectangles.

Here’s another method for making a grid, draw the holes rather than the beams and you don’t have all the crossing edges to worry about.