"Place arm" is an objective in the sidequest Slap-Happy in Borderlands 2
Walkthrough[edit]
Head to the Fast Travel Station and go on out to the The Highlands Outwash. Head on down the hill and toward the river bed in the Hyperion Extraction Plant. Once there jump ionto the water and head to the marker that sits on the Southern end of the plant. There you will find where to hang Sir Hammerlock's arm
