T-H Marine Z-Lock Manual Jack Plate Recent product upgrades, such as the Z-Lock Manual Jack Plate design, secure T-H Marines Hi-Jacker jack plates position as the industry leader. The Z-Locks design reduces the possibility of side slippage while increasing its strength and stability. Constructed of strong aircraft-grade aluminum, these jack plates are stronger and will offer a longer service life, too. T-H Marine Z-Lock Manual Jack Plates are easy to adjust up or down with the center bolt and ca