Wheeler AR Armorer's Bench Block, Gray 156945 Tired of trying to secure your AR parts while installing a pin" detent or spring? The AR-15 Bench Block is the answer! Specifically designed for AR-15 assembly and disassembly" the AR-15 Bench Block is the perfect tool. It securely holds the upper receiver" lower receiver" front sight and charging handle during assembly" disassembly and maintenance.