On 27th Sep 2021 @ 09:45 hrs. While RIH 4-1/2 Wire Wrapped Screen casing, crew make-up 5-1/2” casing elevator into the bails and they make up XO ( 4-1/2 LTC to 5-1/2 LTC ) in the WWS to be used as lifting sub. After latching the elevator driller lifted the joint from the v-door and while lifting it up, elevator lock unlatched & joint fell on to the V-door, One floor man was on the side of the floor holding rope to slow down the joint movement. No injury & no asset damage. Why it happened/Finding : Improper equipment been use “wrong size elevator”. Driller Failed to follow the procedure. ”shortcut”. Floor man did not ensure elevator fully latched. Floor man was in line of fire.