A protective cover assembly for covering a space defined by at least one wall. The protective cover assembly includes a plurality of rails coupled to one another to form a frame for securing a material over the space. At least one support bow spans the space to support the material. Clamp mechanisms are coupled to the ends of the support bow for securing the protective cover assembly over the space. The clamp mechanisms include a latch member for engaging the wall and a handle for biasing the latch member against the wall. The clamp further includes a link for interconnecting the support bow to the frame. A collar is coupled to the link for guiding the handle and the latch member between an operational position and a stowed position along the link.