If you don’t properly anchor your bedding before elevating your adjustable bed, then your flat sheet – and possibly even your fitted sheet – may fall out of place. You may be able to anchor the flat sheet by simply tucking its edges beneath the mattress. If this doesn’t work, consider a flat sheet with corner straps that grip the fitted sheet and provide extra stability. You can also invest in a “sheet suspender,” which is essentially a large rubber band that runs around the side of your mattress and keeps the flat sheet in place.
Each fitted sheet has a “pocket depth,” which refers to the tallest possible mattress the sheet can be used with. If the profile of your mattress exceeds the sheet’s pocket depth, then the elasticated corners can easily slip off. Make sure the sheet and mattress are compatible.