Drat. I just finished a quilt and discovered that the computer missed a small area because of the quilt pattern being cropped. I had already trimmed it so I needed to reload in order to finish quilting the missed area. I pinned tabs of fabric onto the top edge of the quilt to load it onto the take up bar.
Next I used magnetic bars that I purchased at Home Depot to hold the bottom of the quilt. Longarmers call this “floating the quilt” when it's not rolled up onto the longarm bar. They sell the magnetic bars so that folks can screw them onto a wall and pop their magnetized tools in place of drawer storage. Pre-drilled holes make it easy to add knobs on each end. I don't recommend using them without the knobs. The magnets are very strong and manyquilters have smashed their fingers while trying to apply them to the bars on the longarm.
The part of the design that was missing was along the side edge of the quilt and that’s the spot where I needed to attach my side clamps. The clamps would be in the way when it starts quilting. If I attached fabric to the sides my machine would stitch over the fabric and I wouldn't be able to remove the extra fabric I added.
This was my solution. I hand stitched paper to the side edge of the quilt. Next I attached my clamps to the paper then lined up the design to be stitched. While it was stitching the design it stitched over some of the paper. When it was done stitching I easily removed the paper!
I hope this helps you if you need to add quilting along the side of a quilt that was already trimmed.