Instantly a whip-like extension shot out of the other robox, trapped his arm, jerked it away. The pain in his arm where the thing had clamped on it was sharp and shocking. He dropped the tool, yelled.

(Robox from 'Destination: Void' by Frank Herbert)

“What’s wrong?” Prudence demanded.
The whip-like extension slowly unwound, released his arm.
"The thing grabbed me,” Flattery said. His voice was shaky with pain and surprise. “It used its circuit probe . . . grabbed my arm.”
“It won’t let you make the repair?” That was Bickel, his voice coming in loud over the helmet system, indicating he’d plugged into the command circuit from the shop.
“Doesn’t look like it will,” Flattery said. And he wondered: Why doesn’t one of us say what this thing has to be? Why are we avoiding the obvious?
With an abrupt sense of purpose, the other robox reached out a claw arm, lifted the replacement sensor from Flattery’s left hand, matched sensor and socket. Another claw arm recovered the feeler guide, fitted it to the connections of its own circuit probe.