My inventory of items I use.
Intake Sheet (it might even be a Sticky Note)
Tape Measure and attachment devices. In this case two small bungee's on the right.
Tape measure's Hooked Tab on the left.
Now some obvious notations. I have an Innova and the Innova Frame works perfectly with this system and requires very little effort to fabricate. Just another reason why there are quite a few ways to accomplish the same thing. This may not be practicable on your equipment.
Once the tape is fully extended and the quilt is positioned for it's first row of quilting I take note of the left and right edge of the quilt in relation to the tape measure. In this case 34" on the left and 114 5/8" on the right.
I make note of those measurements on the Intake Sheet for reference.
As the longarming process is completed and the quilt is advanced, prior to basting the edges, I keep the alignment of the quilts edges consistent as possible with the measurements recorded on the Intake Sheet. On some occasions the top, left to right, is the same as the bottom. On those occasions when "perfectly square" (oxymoron) isn't applicable keeping the right edge (in this case the 114 5/8") may vary slightly. I focus on keeping the left edge (the 34") measurement consistent from top to bottom.
I use a steel tape, or Carpenter's Tape, for several reasons. It won't stretch like a cloth tape might if placed under tension. Being retractable I can quickly move it out of the way if necessary. On my frame it works well and does not rest on the quilt so it doesn't have to be moved out of the way when advancing. Unlike other methods I've seen the movement (advancing of the quilt) doesn't affect the tapes positioning. Not to mention over the years I've probably acquired a dozen or so. There everywhere I look. I have at least four in the Longarm Room. The one I use is also a one inch wide rule...so the numbers are bigger. Necessary when you can't find you reading glasses resting atop your head.
It has been my experience that when you start putting a lot of stitching into a quilt there is going to be some degree of shrinkage or displacement of size, in one form or another. This system helps me combat that and keeps my finished product as close as possible to the size it was when the piecer finished his/her crafting of the top. It may not be applicable to your equipment, or not suitable to your style of longarming and you may choose not to use a system at all. This is just My Way and it works for me.
Quilt till you wilt...we do.
