A shaped fitter was made from Polymorph. It fits into the last corner of the sheet and is pushed down till the job is done. A cord was attached in case it was pushed down too far and needed retrieving. (Polymorph softens in boiling water, can then be shaped and cut….I used strong cooking scissors…. as required. It hardens as it cools and is very strong).
This young woman could make her bed independently to her satisfaction. She said her mother would like one too!