Faucet Valve Seat Wrench
The faucet valve seat wrench is a simple tool used to remove the faucet body valve seat so it may be replaced.
Compression faucets work by compressing a rubber or nylon washer against a valve seat in the faucet body. Compression faucets are the least expensive and oldest style of faucets. As such they are most common in older homes and where inexpensive faucets are used.
The handle of the faucet is attached to a faucet valve stem assembly. The compression washer sits in its own valve seat in the valve stem assembly. In the base of the faucet body you will find another valve seat against which the washer compresses thereby varying the amount of water allowed to flow through the faucet.
When the washer is allowed to wear down too far, the grinding action between the washer valve seat and the faucet body valve seat can cause the faucet body valve seat to become rough and no longer have a smooth surface, and leaks occur.
When that happens you must either remove the valve seat (simplest) and replace it (using the faucet valve seat wrench) using an exact duplicate, or you must "reseat" or resurface the valve seat (more work).