We used to hold it on the train track but you gotta turn it over before that 2nd boxcar wheel hits so you get even compression also wait for the train cars to be empty because the full load of say gravel will just obliterate the housing.The best technique is to lay in the middle of the track and hold on to a tie so you don't get vibrated all over the place like I did ....... <img src="http://www.catsailor.com/forums/images/graemlins/grin.gif" alt="" />