Imperial Half Moon Wrenches Secure Tools supplies Imperial Half Moon Wrenches. that is designed for use with imperial (inch) measurements. They are specialized tools commonly used in plumbing and pipefitting applications. They are designed for tightening or loosening nuts and bolts with a half-moon or crescent-shaped opening at one end. The half-moon opening of the wrench provides a secure grip on hexagonal or square-shaped nuts or bolts. It allows the wrench to engage multiple sides of the fastener, providing a larger contact area and reducing the likelihood of slippage.