The Thunderbolt is unique in that it offers compression by using the angled deadbolts and often does not require a replacement keep when replacing an existing Winkhaus lock. Available with 16mm wide faceplate and 35mm backset for UPVC and Aluminium doors generally. Capable of replacing locks from 1300mm to 2240mm satisfying a huge range of door heights. Suits UPVC, Aluminium, Timber and Composite Doors. Operation: Split spindle. Latch reversal: Push in latch and a screw will appear in back of lockcase. Undo the screw to remove the latch. Reverse, reinsert and replace screw. Nightlatch reversal: The small rectangular slot adjacent to side of the spindle hole contains a black roll pin. Insert a flat bladed screwdriver and roll the pin to opposite side to reverse function.