A fixed coupler or fixed clamp used in scaffolding is a load-bearing connector designed to join two scaffold tubes at a fixed 90-degree angle.

It is typically made of drop-forged or pressed steel and consists of two half-couplers secured with bolts and nuts. Once tightened, the coupler holds the tubes rigidly in place, preventing rotation or movement. This makes it essential for forming right-angle connections between pipes, vertical standards and horizontal ledgers or transoms.