A form for casting concrete blocks and other products having a resilient insert defining a cavity in which the block is cast and a rigid support or frame for the resilient insert. After the block has cured, the block is removed from the insert either by inverting the form to allow the block to fall from the insert or by lifting the block from the insert. One or more areas of the insert are tethered to the support with at least one generally flat flexible strap so that at least a portion of the insert is allowed to move a limited distance relative to the support and to deform to release the block. One end of each tether strap is embedded in the insert. After the cast block is separated from the insert, the insert is returned to a position wherein it is supported for casting another block.