What was found
NR 2 LEADING EDGE FLAP FAILED TO RETRACT AFTER TAKEOFF. FOLLOWED CHECKLIST WITH NO RESULTS, RETURNED TO PORTLAND. REMOVED AND REPLACED NR 2 FLAP SWITCH, FOUND SPACER MISSING. INSTALLED SPACER, OPERATIONAL CHECK SEVERAL TIMES OPERATIONAL CHECK GOOD PER MAINTENANCE MANUAL 27-81-0.