A collapsible support frame includes a plurality of frame structures each having frame members joined together by a tension cable. A locking mechanism pivotably connects the frame structures and allows a user to move the frame structures between a folded position and an unfolded position. In the unfolded position, the frame structure is locked open and may carry a load. In the folded position, the frame structure is collapsed to form a bundle. A slack control member may provide tension to the tension cable when the support frame is unfolded, and to control slack in the tension cable when the support frame is folded.