Measure the length of the log and make a note of the measurement. Measure the diameter of the log twice, once at each end and note both measurements.
Place the scaling stick across the narrower end of the log, so that the end with the lower end of the scales is even with the point where the bark and wood meet and so the stick passes over the center of the log.
Locate the point on the stick where it crosses the other edge of the log where the bark meets the wood. The scaling stick will have several scales on it, each marked according to possible log lengths. Find the scale that most closely corresponds to the length of the log you are scaling.
Read the figure on the proper scale on the stick where the stick meets the other side of the log. For example, if measuring a log 12 feet long, you would use the scale for 12-foot logs. The number found on scale for 12-foot logs at the point where the stick crosses the boundary between the wood and the bark is the approximate number of board feet contained in that log.