I had wanted a clamp to hold my keyboard on my desk. I found quite a few but the other ones i tried either did not stay on the desk or broke.  This model was inspired by another model on this site called off desk keyboard holder, but i found that it's screws were easy to tighten and that it was made too lightweight even when i printed it out of carbon fiber the part that you clamp to the desk would break.

You might need to modify the file to fit your own desk.  right now it's meant for a desk up to 13 millimeters thick, but basically all you need to do is right click, go to use primitive, click cube, and then basically using those shapes (click on the part itself and click add negative part to add negative space) then right click on the assembly you've made and you can export it to stl, which will perform a mesh boolean which will basically give you an stl of the shape you want.

Another thing worth noting is in my model the screws are sized to 98% of their hole size, so you may need to make the screws a little bit smaller depending on what material you use, i had to use some white lithium grease on mine to get them to go into the threads smoothly, that is in fact why i added the grips to the screws was so that you can be able to turn the thing.  

It's also important that you can slide the thing all the way to the back, the front of the desk should be able to touch the back of the noche otherwise the thing will move back and forth when you use your keyboard or bump it.  

Hope you enjoy it!