Guarded Tool Rest replaces your lathe's toolrest. It is used with the Clark Deep Hollowing System. Its purpose it to keep the hollowing bar from falling down but is only a convenience since you can use the standard toolrest that is supplied with your lathe. It necessary to have one of these to mount the Fulcrum Support Tube however some lathes have a banjo which is too high. In this case, you can get the alternative Guarded Tool Rest. Robust, Oneway, Grizzly among others may need this rest. It your spindle centerline the top of the banjo (with tool rest removed) is under 3.75" then you will need the alternative GTR if you want to use a Fulcrum Support Tube.