These corner brackets are constructed of steel and come in a zinc plated finish. They are designed to repair weak or damaged bi-fold door corners of doors that are 1-3/8 in. thick. These corner repair brackets can be installed on both the top and bottom corners of split bi-fold doors, and they can be used with both 7/16 in. and 3/8 in. Dia pivots. These corner brackets can be concealed from view when installed on the interior side of the bi-fold door. Fasteners are included with each package.