A sheet feed mechanism for a device such as a printer, with a chassis 2 configured to support a stack of sheets 4. A top sheet engaging member 6 for engaging the top-most sheet 40 of the stack and moving it relative to the remainder of the stack 4. A stack engaging structure 8 for engaging the stack 4 and biasing its top sheet 40 against the top sheet engaging member 6. The stack engaging structure 8 having a friction surface 18 extending parallel to the stack engaging structure's direction of travel. A lock mechanism 12 mounted to the chassis 2 for limited relative movement thereto, the lock mechanism 12 having a biased contact foot 32 for engaging the friction surface 18 to secure the stack engaging structure 8 to the lock mechanism 12 for movement therewith. An actuator 20 mounted to the chassis 2 to disengage the contact foot 32 from the friction surface such that the stack engaging structure 8 moves relative to the lock mechanism 12 to press the top-most sheet 40 against the top sheet engaging 6, then the actuator disengages the contact foot 32 such that it re-engages the friction surface 18 and then moves the lock mechanism relative to the chassis 2 such that the stack engaging structure 8 also retracts a predetermined distance from the top-most sheet engaging member 6.