You can buy self adhesive velcro that can be cut to the desired length and then it tapes itself to the sheet and mattress. I would recommend also stitching the sheet side of the velcro unless you air dry your sheet. The high heat in the dryer will cause the adhesive to eventually let go.
Hi Bobbie! I agree with Kathy, but, I would zigzag around the edges.
Are you referring to the project tease posted today? Just click on the tease line and project will open for you.