Following our step-by-step AR-15 lower receiver build?
If you’ve left off from installing your bolt catch, let’s go through installing the pivot pin (like these). If you need more detail on any of the tools or components I use in this step, you can look over this list.
(09:20) Step 4 – Pivot Pin
Drop the spring into the hole on the front of the AR-15 lower receiver. Now grasp the detent with the needle nose pliers and gently push the detent downward onto the spring. Without releasing the spring tension, slide that razor blade over the detent and release the pliers. If you did this correctly, the detent will be trapped under the razor blade. If you did this part incorrectly, I wish you the best of luck in finding your detent (you may just want to pick up a few backups, just in case).
Slide the pivot pin in and out. Does the detent stop it from coming completely out of the receiver? Nice. Trigger installation, here we come.