Underlays are placed between the mattress and the slats where they reduce friction and help prolong the life of the mattress.
They can also create a more cosy sleeping environment by keeping away cold air from the mattress.
Although underlays are designed to protect the mattress from the slats, they can be used on top of the mattress as a firming topper that reduces the feel of any lumps, bumps and springs in your mattress! This has been tried and tested at Greenfibres!
Underlays are particularly recommended for mattresses made from latex which are prone to indentations.