This is a remix from a model designed by Mussy. He had a great version of this already created, but it was quite tight when trying to place it on a common picatinny rail, and while I like the vertical securing holes as an option, I generally stay with M4 bolts at a minimum and find a horizontal securing option much easier to manage for most applications.
This was remixed for placement on an airsoft rifle, but could easily be used for real steel as well.