This bed-sheet holder features a coordinated “base-plus-sleeve” dual-component design, leveraging mechanical fastening principles to ensure long-term, stable adhesion of the sheet to the mattress:

• The larger lower component (the base): Designed as a flat structure that matches the mattress thickness, it can be securely pressed against the underside of the mattress; its protruding cylindrical fixing end provides a “nested fulcrum” for the sheet, using friction between the sheet fabric and the cylinder’s surface to initially constrain its position.
• The smaller sleeve component: Constructed as an open-ended cylindrical tube that slips over the outer surface of the base’s cylindrical end, it enhances the fixing effect through physical constraints—preventing the base’s cylinder from slipping out of the sheet’s opening while, at the same time, the dual clamping action between the sleeve and the sheet further resists any tendency for the sheet to slide.
• It is recommended to print this part using PETG; for optimal results, install two units at the corners of the mattress.