The cost for the tools used during the build will be calculated based upon how long the operator(s) were in the 10’x10’ area.  If it takes 10 minutes to build your system, all of the tools used will be pro-rated for those 10 minutes.  For example, if you use a pipe wrench ($5.00 per unit-hour), and the build takes you 10 minutes, the cost for the pipe wrench is ($5.00/60 minutes)*(10 minutes) = ($0.083/minute)*(10minutes) = $0.83.