The ROugh MIll simulator (ROMI Version 3.0) is a computer software package for personal computers that simulates current industrial practices for rip-first and chop-first lumber processing. This guide shows the user how to set up and examine the results of simulations of current or proposed mill practices. ROMI-3 accepts cutting bills with as many as 600 combined solid and/or panel part sizes. Plots of processed boards are easily viewed or printed, as are detailed summaries of processing data (number of rips and crosscuts) and yields for each grade.