A hook is a downturned or shaped section at the panel edge that locates in a rebate in the kerb or frame. It stops the panel sliding, resists uplift when a wheel lifts the trailing edge, and still allows the panel to be lifted vertically for cleaning.

Getting it right requires the kerb dimension as built, not as drawn. Concrete moves during the pour, rebates are formed with timber that swells, and a hook made to the drawing frequently does not fit the thing that was actually cast.

A hook that is too tight will not seat, and someone will grind it on site. A hook that is too loose lets the panel move, which is the rocking failure described elsewhere in these notes. The tolerance band between those two is narrower than most specifications acknowledge.

So measure the rebate before ordering, and send us that measurement rather than the design dimension. Where the rebate has not been cast yet, we can supply the panel and the frame together, which removes the problem entirely because both are made to the same number.