I built a set of flip up sights and a free floating quad rail that interfaced with my Model 1 AR-15 to add an accessory rail that looks great and is functional. I got many of the parts from www.3dcontentcentral.com
but everything highlighted in blue in the main picture were parts that I designed and made.
I started by building any jigs needed. The tricky part was cutting out the 45 degree angles on the sight clamps for the picatinny rails. I built a 45 degree angle jig since I did not have any mitre tooling for the mill. Then made temporary attachments for the sight pieces to attach to the jig. I made the jig using some corner brackets and clamped that into the mill. It made for a very nice jig.
The .pdf files show the parts that were created and any jigs needed to make all of these parts.
The quad rail was built as an assembly using 4-40 and 8-32 hardware holding it together. It was then cerakoted black. I used a 1/4" ball end mill to smooth the transitions between angled surfaces.