Platform twin beds – Fabric sheets, which are sold in wide widths in fabric stores, surrounded by turns in a flat sheet of DIY perfectly designed for your bed. A few cuts and straight stitching lines, and a flat sheet becomes installed at the corners. The same trick that turns a flat sheet home made into an adjustable sheet can be used to make any commercial flat sheet equipped as well. Cut sheets of fabric to 67 by 106 inches. Press a 1/4 inch hem on both long edges of the fabric. Fold and attach an additional 1/4 inch in and sew this hem in place with a sewing machine. Repeat at the lower short edge of the sheet.
Make platform twin beds, press a 1-inch hem along the top edge of the blade. Fold and iron a second, 9-inch hem on the same edge. Pin this hem, and then sew through it. Make a second flat sheet to use in making an adjustable sheet. Place a corner of a flat sheet on a grid cutting mat. Measure and mark a point 13 1/2 inches from each side of the corner. Draw a 13 1/2-inch line from each of these marks, making a square. Cut the square with scissors. Repeat on all four sides. Bring the sides of each corner cut together and pin. Sew along these seams. This turns the flat sheet into an adjustable box-shaped sheet.
Cut four pieces of 1 inch non-elastic roller, 12 inches each. Pin one end of a piece of elastics 6 inches from a corner of the sheet, with the bottom edge of the sheet aligned with the bottom edge of the elastic. Sew the elastic to the sheet, stretch the elastic as you sew, until it reaches 6 inches on the opposite side of the corner. Trim elastic excess. These points to the fabric in, elasticity to the corner. Repeat at the corners to make an adjustable sheet. Then, platform twin beds already use.