Whenever I use the wood lathe I use any of these spacers for adjusting the height of the tool rest; they are made out of 7/8" nuts (from leftover plumbing), to which the inner diameter is enlarged on the lathe (Unimat) to easily enter on the post.
The height of the nuts is 3/4"(white), 5/8" (bronze) and 7/16"(black). This way you adjust the height you want to place the tool rest, according to the tool to be used. The color of the spacer helps systematically identify the one required.
Distance from the tool rest to center:
without spacer: 3/4"
black spacer: 5/8"
brass spacer: 3/8"
white spacer: 0"
This system is more practical than putting marks on the pole for the setting, or than putting a collar which adjusts to different heights, and of course, more practical than the method of manual adjustment by trial and error.