CrossTac AR-15 Armorer Block
The CrossTac AR-15 Armorer Block is reversible block that will fit both upper and lower receivers on an AR-15 and hold it for gunsmithing tasks. I’ve assembled and disassembled quite a few AR-15s over the years, and have found that some kind of specialized aid that holds the parts in place is much more convenient than wrapping them in a cloth and sticking them in a vice. It also prevents damage to the components.