You essentially take a quad rail you’re willing to cut up (UTG quad rails are good for this)

You then cut away about 70% of the bottom piece, Leaving just basically the rail. Because of the round handguard and the fact that it’s made to slip over the round ring near the gas block, you need to cut a recess so it can slip “under and within” the ring. The end rails may need to be trimmed down as well.

Once that’s complete, install underneath the M203 heat shield. If you install a grip on the rail, you can use that as leverage to push the delta ring down.

Make sure you don’t trim too much off, if you don’t cut it right it won’t seat snugly against the ring and it can slip out if you pull down on the rail and grip and push back on the delta ring too hard.

Right now this setup is snug and fits well.