Desk shelve support

I needed a monitor shelf, but i wanted it to be the entire width of my desk (120cm) and wider than is possible to make out of one piece with my prusa Mk3.
I also wanted it to have a little tab to be stuck behind my desk so it wouldn't come forward.

the width was based on a plank i had in stock so I just had to trim the length to fit my desk (120cm)
width of the plank that is able to fit right now is 31cm. 
at the back is space for a screw to hold the plank, but i opted to use double sided tape instead on my own shelf.
spacing on the key slots to fit it together is rather tight…. I didn't need any glue and its quite hard to get it out so I went with it.
maybe adjust it if your printer is not that accurate.

I added a center piece, because my plank was sagging in the center, you will not need this if your overhang / weight on the plank is not as much as mine

specs:
design for 18mm thick plank
design for 31cm wide plank
adds 13cm height (including plank)
thickness of the print is 2cm
 

I used PLA (generic) with 0.2mm layer height