Abstract: This invention relates to a device and method for forming in situ cast reinforced concrete slabs, with removable forms and incorporating the upper portion or chord of a joist as in integral reinforcing member. Relating to a method and device that allows adjustable thickness concrete slabs to be cast in place by means of adjustable hangers, which are particularly adapted to work together, with a bar or beam form support for temporary form-sheets, in a substantially leakproof manner in conjunction with the upper portion or chord of a standard open web bar joist.