no instructions with any of my B&T stuff.....and I have tons! Intended for Police/Military armourers who should have enough on the ball to figure this stuff out....lol. Very easy to install all their quad rails (SIG 552, M4, G36C,etc,etc). I did not let the spacer block on the M4 rail touch my barrel though....didn`t want it to scuff the finish if I decide to remove the rail at some point. the spacer block is the little block with the chamfer that matches the barrel profile. It is mounted using a small screw to the inside bore of the quad rail. Used to stabilize the rail with contact on barrel.Used approx .005 clearance with barrel to allow for thermal expansion and still no contact.