A binding strip and post clamp construction for expandable looseleaf binders utilizing posts of a stiffly flexible rodlike character, comprising a folded two-ply strip of resilient coverboard material with registrable holes and a clamp of stiff springy material slidably engaged on the strip, a lower plate of the clamp underlying the strip, a bight portion engaging the fold thereof, and a parallel upper plate having a free edge reversely hooked to receive the edge of the upper ply for guided clamp movement and to frictionally grip said lower ply between the plates, the upper plate also having a post receiving channelled section for sliding over terminal end portions of posts flexed against the strip. The clamp is slidable into position endwise of the strip.