Every tutorial I've ever seen on assembling a quilt sandwich tells you to lay the backing out on a hard surface: your giant, attractively tiled kitchen floor; those several large folding tables that you keep stored in your ample basement; your living room's reclaimed oak or ecologically-responsible bamboo floor. For those of us who live in smallish apartments with crappy wall-to-wall carpet, this doesn't work well.
I've been assembling quilt sandwiches in my kitchen. At the widest point with available floor space (i.e. not under the table), it measures about 5' across. This works fine for putting together small or lap-size quilts. Larger quilts have to be assembled in the living room, where there is floor space, but where there is also carpet. The backs of quilts assembled in my living room have up-till-now contained puckers and wrinkles because I couldn't get them to stay flat.
I was thinking about putting together the quilt sandwich for my blue quilt and wondering where I could go to lay it out on a hard floor (my mother's house? school? the grocery store?) when it occurred to me that all I really needed was tent stakes. Well, not literally tent stakes, but that idea: something to hold the backing fabric stretched out on the living room floor.
I decided to try using my largest size of safety pins. I stabbed them through the backing fabric and into the woven part at the back of the carpet. It actually held quite well.
I didn't take a picture of just the backing fabric for the blue quilt because it's large enough that, in order to fit it all into the frame, you wouldn't be able to see the safety pins. Here's a smaller-size reproduction:
If you look carefully, you can see the pins at the top and sides of the fabric. I "staked" the backing down, then went back and repositioned the pins to pull any loose areas tighter.
After pinning, the back seemed to be quite flat. I'll post after I finish quilting with a pucker-and-wrinkle-report.