PMSL. its called that because when you are doing a drill ride/mucial ride/ group display you checking your postition in relation to the other riders is called checking your dressing. if you are getting uneven the ride commander should tell you to dress to the left or right which ever is appropriate. and i think it comes from the military. because of that when you jump a dressing fence you should be level with the other rider(s) sort of knee to knee.