USP Rail Adapter
If you've handled a USP, you know what this is for.
This is an adapter that puts a chunk of picatinny rail under the HK USP proprietary rail. This actually works, but because it's meant to be a snap-on/snap-off design, it is not rigidly mounted. I would only recommend using this for flashlights. It won't hold zero if you throw on a laser. Also, it's designed for a USP 9mm Full Size. If you have the .45 or a Compact, you may need to modify this a bit.
Find out more about this design and others on my blog http://www.printedfirearm.com
[Built off of Thomas Harold's picatinny template]
Original design by Noah