The SASC are specialist Corps of Sergeants and above who traditionally specialised in the delivery of Skill At Arms and Fieldcraft although they are now involved on all aspects of training including design, deliver and validation as well as a myriad of other areas (coaching, advisory)linked to training for operations. There is no direct entry so you have to join up with another capbadge (Infantry, RLC etc) and then get recommended either on a course report or via your annual report, pass their selection at Breacon and then you are re-badged SASC as a Sergeant. Hope that's useful.