Abstract: A mast track clutch assembly allows the longitudinal position of the mast of a windsurfing sailing board to be adjusted by means of a foot pedal. The mast is attached to the clutch assembly, which is movable in a longitudinal track on the sailing board. The clutch assembly includes a pressure plate that is biased to retain the assembly at one position on the track. A foot pedal is operable to move the pressure plate against the bias, allowing the longitudinal position of the mast on the board to be adjusted by the board user while the board is in motion.

Abstract: The invention provides a simple, economical and effective means of constructing a retaining wall from conventional concrete building blocks. A sheet member is provided, having protrusions which locate in the hollow core portions of the blocks to couple the blocks together. Where a tie-back is desired, the sheet member has an anchoring portion which extends back into the backfill to anchor the wall thereto. In one embodiment, the sheet member is plastic or other non-corrosive substance, with a matrix of dome-like protrusions. In another embodiment, the sheet member can be of a mesh-like construction. In another embodiment, the anchoring portion can be corrugated, with the corrugations running parallel to the wall. In another embodiment, the sheet member can be a sheet of stainless or galvanized steel or the like, or other suitable material, with tab portions stamped therefrom to form the protrusions.