B737-700 #1 ENG CORE COWLING WAS DAMAGED WHEN THE TECHNICIAN OPENING THE COWLING WITH A HYD PUMP CONTACTED THE LEADING EDGE DEVICE PREVIOUSLY DEPLOYED BY THE TECHNICIAN.

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SCHEDULED WORKLOAD FOR ACFT X WAS A SVC CHK #1 ENG FAN FRAME INSPECTION; ALTIMETER MANUAL REPLACEMENT; DEFIBRILLATOR BATTERY REPLACEMENT. UPON ARR TO ACFT; I SVCED ENG OIL; CHKED TIRE CONDITION AND PRESSURE AND WIPED STRUTS. I CHKED LOGBOOK AND TURNED ON EXTERIOR LIGHTS AND WALKED AROUND ACFT CHKING LIGHTS AND CLRING FLAP AREAS FOR DEPLOYMENT. I TURNED OFF LIGHTS AND LOWERED FLAPS FOR EXTERIOR WALKAROUND; ALSO RAISED SPOILERS. I WALKED THROUGH CABIN; SVCED LAVATORY WASTE LINES AND PERFORMED OTHER INTERIOR AND CTL CABIN INSPECTIONS. ONCE FINISHED; I BEGAN EXTERIOR WALKAROUND INSPECTION BEGINNING ON CAPT'S SIDE AT RADOME; AND PROCEEDED TO ENG AND OPENED INBOARD AND OUTBOARD FAN COWLS. SHORTLY AFTER MY LEAD ARRIVED TO CHK ON THE ACFT AND SEE IF I NEEDED ANYTHING; I ASKED HIM TO CALL QUALITY CTL TO LET THEM KNOW I WAS READY FOR THE #1 ENG FAN FRAME INSPECTION. LEAD CALLED AND INFORMED THE INSPECTOR. CONTINUING THE WALKAROUND INSPECTION; I REALIZED I NEEDED TO OPEN #1 ENG OUTBOARD CORE COWL FOR THE FAN FRAME INSPECTION. JUST THEN INSPECTOR ARRIVED AND I TOLD HIM I NEEDED TO OPEN THE CORE COWL AND I NEEDED TO GET A CORE COWL PUMP. INSPECTOR SAID NO PROB; AND I LEFT TO GET THE PUMP. WHEN I RETURNED I PROCEEDED OPENING THE CORE COWL; DURING WHICH I NOTICED OIL LEAKING FROM THE CONNECTION AT THE OPENING ACTUATOR. I TIGHTENED A LOOSE 'B' NUT AND CONTINUED OPENING THE CORE COWL; NOT REALIZING THE CORE COWL WAS CONTACTING THE #4 SLAT. I PUNCTURED THE AFT OUTER SKIN OF THE CORE COWL. I BELIEVE WHAT CONTRIBUTED TO THE EVENT CAUSING THE DAMAGE WAS I BECAME OUT OF SYNC NOT COMPLETING THE WALKAROUND INSPECTION BEFORE PERFORMING THE FAN FRAME INSPECTION. HAD I COMPLETED THE WALKAROUND; I WOULD HAVE FINISHED BY RAISING THE FLAPS AND SLATS; THUS PROVIDING CLRNC TO FULLY OPEN THE OUTBOARD CORE COWL.