The handing is defined by viewing the door from the pull side of the door or casement.

Click links for relevant diagrams:
PANIC HARDWARE
MORTICE LOCKS
RIM LOCKS
CUPBOARD LOCKS
LEVER & PULL HANDLE FURNITURE
CASEMENT FASTENERS
ISO HANDING

Click links for relevant videos:

Re-handing of Panic & Emergency Bolt SED992 & SED994
Re-handing of Panic & Emergency Latch SED991 & SED993
Re-handing of Outside Access Device with Knob SED990
Re-handing of Outside Access Device with Lever SED900
Re-handing of 3 Point Panic Bolt SED912