Wray - The air planishing hammer , allows you to detail small areas, something which the English wheel does not do well.
Air is used to reciprocate a small piston very rapidly.
The bottom arm is the anvil. This type of air planishing hammer was a common tool in all automobile and aircraft repair shops, from the late twenties to the 1960s. When bondo came into practice fixing imperfections , became filling imperfections. Wray - The powerhead that I use was originally attached to a small light tubing frame. You would take the tool to the work.