A B737-400 ON APCH AT 8000 FT WHEN SPOILERS AND FLAPS WERE DEPLOYED A PAX RPTED A CORDLESS SCREWDRIVER IN THE R WING.

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DURING OUR ARR TO ZZZ VIA THE RNAV APCH WE WERE INSTRUCTED TO HOLD AT 8000 FT AWAITING THE DEP OF A LIFEGUARD LEARJET. AFTER 2 TURNS IN HOLD WE WERE CLRED FOR THE APCH. WE WERE ABOVE THE VNAV PATH DUE TO THE HOLD AT 8000 FT; AND IMMEDIATELY LOWERED THE GEAR AND DEPLOYED FLT SPOILERS TO REGAIN PATH. THIS APCH WAS LATER TURNED INTO A VISUAL UNEVENTFUL APCH AND LNDG. NO ABNORMAL INDICATIONS WERE OBSERVED. DURING DEPLANING; ONE OF OUR DEPLANING PAX MENTIONED THAT THERE WAS A CORDLESS SCREWDRIVER LAYING UNDER ONE OF THE SPOILER PANELS ON THE R WING. INITIALLY WE WEREN'T SO SURE AND CONDUCTED AN INSPECTION FROM THE CABIN WITH THE SPOILER UP; AND VIA A LADDER. SURE ENOUGH; THERE WAS A CORDLESS DRILL SITTING THERE. WE CALLED MAINT; AND THEY REMOVED THE DRILL. THE FLAPS HAD TO BE EXTENDED TO F1 TO RELEASE THE DRILL. NO DAMAGE TO THE DRILL'S PLASTIC CASING WAS OBSERVED. MAINT CONCLUDED THAT THERE WERE MINOR DAMAGE TO THE FLAP LEADING EDGE; SMALL DENT IN SPOILER PANEL; EVIDENCE OF PRESSURE ON THE CANNON PLUG FOR THE FLAP SENSOR; AND A SCRATCH IN THE SPAR. MAINT WORKED WITH MAINT CTL AND THE DAMAGE WAS FOUND TO BE WITHIN LIMITS VIA TESTING; MINOR REPAIR; AND AN ENGINEERING ORDER. AFTER CONCLUDING REPAIR AND PAPERWORK; WE FERRIED TO ZZZ1. ALL INDICATIONS WERE NORMAL. I WAS SURPRISED TO LEARN THAT TOOLS ARE NOT CHKED OUT/IN DURING REGULAR MAINT AND REPAIR. THAT WOULD HAVE MITIGATED THIS ISSUE. I BELIEVE THE WORST THING THAT COULD HAVE HAPPENED AERODYNAMICALLY WOULD HAVE BEEN A SPLIT FLAP/NO FLAP LNDG. THE REAL DAMAGE COULD HAVE BEEN DONE WHILE THE FLAPS WERE EXTENDED DURING TKOF OR LNDG BY THE DRILL FALLING TO THE GND HITTING A PERSON OR PROPERTY. ONCE THE FLAPS WERE UP; THE DRILL WAS 'LOCKED' IN PLACE. SUPPLEMENTAL INFO FROM ACN 697499: IN LOOKING BACK ON WHAT TRANSPIRED THAT MORNING I CAN SEE THAT WE DID NOT ADEQUATELY ACCOUNT FOR ALL THE TOOLS THAT WE HAD TAKEN OUT TO DO THE JOB AND THAT WE DID NOT DO A LAST GENERAL INSPECTION OF THE AREA OR A LAST OPS CHK OF THE FLAPS. I THINK THAT BECAUSE WE ALL WANTED TO GET THE JOB DONE; WE NEGLECTED TO SLOW DOWN AND CAREFULLY REVIEW THE COMPLETE JOB.