Us hybrid or pop-up RVers call the pole that holds up the bunk bed canvas is referred to as the shepherds pole. That was on my old Aerolite (2005) hybrid, my newer 2013 Aerolite hybrid also has the same 3 hole bracket that allows you to abjust the height of the bunk bed thus keeping the canvas taut. So if you move the cable one hole down on the bracket, that will lower the bunk bed about 3/4" which will tighten up the material. You just don't want the material too tight because it will start to "pull" the material near the roof line like in this
picture