I use blocks of scrap wood for box heights and string when alinement us critical like rows of lights. Floors are lot more level then top plates are straight. Did a show room once where ever other light was 4 foot track and the the rest was 4 foot wrap arounds. Add to the fun the lights ran at a 45 degree angle to the walls. Used string to rough in the boxes and to hang the lights. Everything was laser straight.
