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Servo-arm
From Warhammer 40k - Lexicanum

Servo-arm of the Space Wolves' Iron Priest, with its jaws cast in the shape of a Fenrisian Wolf's head
A Servo-arm is used by Space Marine Techmarines to help repair damaged vehicles on the battlefield. It can also be used as a devastating weapon in close combat.[1]
A Servo-arm is, to all extents and purposes, a large mechadendrite.[1]
Related articles
Sources
- 1: Codex: Space Marines (6th Edition), pg. 122