Ship to shore (STS) cranes handle millions of containers every day. One of the latest products from Stinis is the Split-Headblock. This device allows its user to work in tandem operation in which up to two 20ft or four 40ft containers can be lifted at once. In order to further increase the performance, it is important that it can be accurately positioned. Due to wind, trolley driving, and possibly other factors, the Split-Headblock starts to skew. This motion makes it very difficult to enter a cell on a ship or place the containers onto truck trailers. Reducing the skewing motions can therefore increase the cranes performance. Several attempts have already been made to control this motion from the crane. This research proposes a method to control the skewing motion from the headblock. A solution is proposed where horizontally movable sheaves are controlled with a PID controller to control the system. Tests are performed with a Simulink Simscape simulation model. The solution has been tested on a variety of load cases, hoisting heights and external disturbances. Out of the 124 cases tested, 86 showed a successful outcome where the anti-skew system is an improvement compared to not using the system. Taking all results into account, the anti-skew-system can improve the number of MPH and total throughput up to 6% in least favourable conditions and up to 17% in most favourable conditions.