Modern servo drive technology makes it very easy to reliably synchronize electronically. This is often the best approach as it saves a lot of mechanical assembly and alignment. Belt driven slides may be linked with a drive shaft between the two units with the motor either outboard of the pair of slide or driving the shaft directly. Screw driven slides may be linked with a timing belt or chain but the tension is limited by the maximum radial capacity of the input shaft on the slide. They may also be linked via right angle gearboxes on the inputs and a drive shaft between the two gearheads.