Check out this Picatinny vice block from KE Arms. It allows you to lock your ARs upper receiver in a vice via the Picatinny rail and is pretty handy when trying to align your rail and upper during installs. I swap rails on my ARs all the time and it can be a pain for some types of rails, especially if you you don’t lock the upper down in a vise or don’t have someone else helping you with a second set of hands. At just $9.95 the KE Arms vice block is a small investment that will make your life a whole lot easier if you plan on swapping out rails often. Check them out at kearms.com.
Secure your upper receiver in a vice with the picatinny vice block. This block can also be used to line up the upper and rail of your firearm to ensure accurate alignment when installing the rail. Made from injection molded polypropylene.
[Source: Jerking The Trigger]