You could try using safety pins.
You don't. Those things are made to drive the normal person insane! : ) Make a garter belt for your sheets.
You may need to buy deep pocket sheets if you have a thick mattress... that should help!
You can buy elastic bands that you attach to the corners of the sheets so they can’t come off at the Dollar Tree.
Get velcro strips..Works for me
Sheet garters do work assuming the sheets are deep enough for the thickness of the mattress. Attach them as far away from the corners as possible.
Buy nice deep ones. I love the Threshold brand from Target. They stay on and are nice quality, but affordable.
Sewing 2" wide elastic bands, with corners cut at opposing 45 degree angles to the corners of the fitted sheets will cure your problem. There are some excellent You Tube tutoriaks for this.