A STOPPED B737 STARTS ROLLING BACKWARDS FROM ITS GATE PARKING POS WHEN THE PIC STARTS ON THE ACFT PARKING CHKLIST BEFORE SETTING THE PARKING BRAKES AT ZZZ.

Narrative

AFTER ARRIVING AT THE GATE WITH THE ENGS SHUT DOWN WE WERE RUNNING THE PARKING CHKLIST WHEN WE NOTICED THE JETWAY SLOWLY MOVING. AT FIRST I WAS NOT SURE IF IT WAS MOVING OR THE ACFT WAS. I REALIZED IT WAS THE ACFT AND APPLIED THE BRAKES TO STOP MOVING. WHAT I HAD DONE WAS TO HOLD THE BRAKES IN ANTICIPATION OF A QUICK CHOCKS IN PLACE SIGNAL FROM THE RAMP; AS USUAL; INSTEAD OF SETTING THE PARKING BRAKE. APPARENTLY MY FEET SLIPPED DOWN THE RUDDER PEDALS AS I WAS DISTR FROM DOING THE CHKLIST AND LOGBOOK FUEL ENTRY. THE ACFT MOVED ABOUT 2-3 FT BACKWARDS. I CHKED WITH THE RAMP PERSONNEL TO DETERMINE NO ONE WAS INJURED OR ANY DAMAGE OCCURRED -- ALL OK JUST STARTLED. THE FOLLOWING THINGS COMBINED TO CONTRIBUTE TO THE SIT: WE RAN THE CHKLIST TOO SOON. I SHOULD HAVE SET THE PARKING BRAKE. I ALLOWED MYSELF TO GET DISTR BY COMPLACENCY AND HURRYING TO GET THROUGH IMMIGRATIONS AND CUSTOMS. ALSO; SOME KIND OF NON-SKID SURFACE ON THE RUDDER PEDALS WOULD BE NICE. THIS KIND OF THING CAN SURE GET YOUR ATTN TO HUMBLE YOU AND MAKE YOU RESOLVE TO BE AS CAREFUL AND VIGILANT AS POSSIBLE.