Carbine Doncaster Entance Exterior Knob & Interior Lever SetCarbine 4000 Series entrance exterior knob & interior lever set adjustable 60mm 70mm backset. Carbine have developed the combination knob and lever set in various functions. It's a combination of the round Sandown 4000 knob series on the outside and the lever of the Rosehill 6000 series on the inside. As such, it is a tie bolt function. Function Outside Opened by knob when free. Key unlocks both knob and lever but does not retract the latch. Inside