i have one of those that i bought at farm auction in PA. mine doesn't have legs. elders at the auction said this style was meant to sit on chair backs or suspended from cieling. i use dining chairs and c-clamps to hold the corners. i replaced the original leaders that were so old they almost disentegrated when touched
. the corners of each of the polsa are densely dimpled from many decades of quilting.
i cannot sit at a frame because of back problems, so i use the frame to hand baste quilts for hand or machine quilting. remove & put frame poles away until needed again. when basting i attach the back with even tension all four sides. i then slide the outer rails a bit if needs to be tighter. then lay out the batt ..then the top. if quilt no larger than double or queen size i reach as far toward center to start the basting, then work alternating sides until i'm out to edge. i learned the technique from book. they said to do giant cross from alternate corners across surface then horizontally & vertically. i used to do that but decided it keep it square like they said it would. i thread baste about every 3-4". if you want more on how i attach & set up pm me.