JACTON offers top quality worm gear screw jacks with ball screw and trapezoidal screw. The trapezoidal screw jacks have self-locking function while ball screw jacks do not have self-locking function. Note: the trapezoidal screw jack's self-locking function has relationship with the pitch, large pitch with lower self-locking, larger speed gear ratios with higher self-locking function. To ensure self locking in worm gear screw jacks completely, the brake motor is needed.