Description: Side mount Base  Full Metal Construction  Attach to 20mm Standard Weaver Base  .DO NOT overtighten the mount. If you cannot close it with just moderate force, you've tightened it too much, you must back off and readjust the notched adjustment nut. There is also a retaining "plate" the keeps the locking latch from working loose ( this is nice touch!) and you should tighten down this plate once you are satisfied that it is securely keeping the latch in place.There is also a split bolt that prevents the sight mount from ever working loose.I'd add on this . Actually .I would suggest using on all screws and nuts once you get your sight mount right for you. Remember to take your time and do the correct adjusting that is not too tight. If it is loose you'll know immediately.Too tight and its impossible to close the locking latch.