How to cut-through a polygon in AutoCad 3D

[Anonymous]

(Do not know what this "select a board" option is for, so I went with Drafting Techniques?)

Hi, I have created a bookshelf which is symmetrical on each 4 sides of the inside of a room. The shelves are symmetrical and are joined by mitre joints. 

I want to show this in 3D so after joining the four sides of the bookself sets, I need to cut through the 3D created shelf units - through the corners for them to join as a mitre. I hope this makes sense?

I am very new to AutoCad 3D, but a regular at AutoCad and SketchUp, but am struggling with learning this 3D side of AutoCad, please help.

Greatly appreciated!

Please see below attached image of the bookslef plan view -

TO CLARIFY: I need to know how to cut through each corner making it look like the right visual of the bookshelf, but in 3D I must cut though and do not know how

[parkr4st · Accepted solution]

try the SLICE Command

[Anonymous]

Hi, thank you I did but I do not know how to...

[Anonymous]

 Parkr4st - thank you I thought I used that option because I tried every icon on the toolbars, but it was not on the toolbar acutally so I typed it in and figured it out eventually after finding it from the command bar...it worked beautifully!

[parkr4st · Accepted solution]

push F1 for help and search for slice.  It is nicely explained there.  Try it and repost your progress and your drawing if there are further questions