Kitchen and bathroom sink faucets typically are secured with low-profile mounting nuts that are accessible only on the underside of the sink, behind the basin. Standard wrenches and pliers are almost useless in this situation
A basin wrench has a pivoting gripping head that sits at the end of a long handle, and it is designed to reach up into that awkward, inaccessible space behind a sink to tighten or loosen the mounting nuts on a faucet or the flexible supply tube nuts that connect to the end of the faucet tailpieces. These nuts are so difficult to reach that some plumbers prefer to attach the faucet to the sink or countertop before setting the sink or countertop into place. Where this isn’t possible, though, the basin wrench lets you reach up behind the sink from underneath, grip the mounting nuts, and tighten or loosen them easily.
