This is a drawing Dick did for scene 4x:This drawing is from scene 5x:
TB means trace back. His feet in this case did not move, for a while at least. I couldn't put them on a held cel because his leg had to move, so for the linetest I roughly traced them for each drawing from drawing 143, probably in green. TB 143 told the tracer to trace back the foot for each cel to drawing 143, but he had to do it with much more care. Later in the scene there were indications drawn in red pencil: Match BG. Parts of the Thief were going behind the rock in shape of a thumb. Here the tracer had to first trace himself a master match line from the final background and then trace a self ink line in the color of the coat on each cel, "matching" it to the BG. The color red was always reserved for this, so that T&P would know right away what to do.
There were a lot of rules like this. Over the years Dick had streamlined the processes used in his studio to ensure good product.
This drawing appears to be an inbetween by the way. Keys had the drawing number circled and usually a chart on them. Looking at this drawing reminds me of s.th. Dick once said about the Thief style. Animation drawings and linetests often look best in the rough stage and sometimes lose a bit of appeal at every stage until they reach final color, while the Thief scenes tended to look best once they were painted. Maybe some of that's due to the 2 dimensional style. The Thief's coat also reads much better as a shape once it's painted. Dick often would shade in the coat on the animation drawings to aid a better read of shape as opposed to lines.
In an earlier post there is an image comparison illustrating the evolution from rough to final. The example is a bit extreme because in many scenes Ken's version was closer to what ended up on screen, but it shows the general trend of scenes improving in final. Click LINK