Algodoo

Left and Right arrow keys to move the extender left and right, respectively.
Up and Down arrow keys to open/close the claw. Press the Down arrow key once to have it clamp down, and press again to have it release.
W and S keys for raising and lowering the claw.
Press B once to have the whole mechanism move backwards.

Note: Don't extend it too far, because it might have problems retracting. If it does, try "wiggling" it by alternating the left and right arrow keys.