Some will have a fetal rig attached directly to them, then each rig will be compatible with a few types of machine for that sector. Other specialist fetus's will be implanted straight in to the machine.
This is a loading test for a fetal rig. The idea is the rig with the appropriate rig attached is sent along a series of conveyors/sliding racks to the desired machine. This will probably be for a section of the mechanical beings, maybe a sector which needs a fetus capable of multitasking.