Electrical controller for roofing apparatus

A controller for propelling a carriage along a plurality of purlins, and method of using same are disclosed. A plurality of carriage sections are joined to form a continuous carnage spanning a plurality of purlins. A plurality of puller assemblies are attached to selective ones of the carriage sections. A controller is connected to the plurality of puller assemblies. The controller can be actuated to a master control mode which simultaneously engages the plurality of puller assemblies, thereby propelling the carriage along the purlins. The controller can also be selectively actuated to a selective mode which engages one of the puller assemblies.