A strapping device used for installing, supporting, and sealing under-mount sinks comprises a series of straps looped by a series of rings and locking tightening devices. The locking tightening devices are used to tighten the straps and raise and support an under-mount sink in position. The rings and straps are anchored to hooks attached to the edge of the sink opening on the counter top underlay. A series of hooks are capable of holding a series of straps under tension to support an under mount sink in position with a located on the lip of the under-mount sink. A continuous loop of closed cell PVC is disposed atop the lip of the sink, so that when the sink is tightened through the countertop underlay, the lip of the sink encounters the underside of the countertop and the sealing material is compressed, forming a permanent, flexible, water-tight seal.