A bouldering mat or crash pad is a foam pad used for protection when bouldering. There are various sizes and makes, but the most common type is a folded mattress, thick, that when unfolded measures about . Most of bouldering mats often have shoulder straps so as to easily move it between boulders. Bouldering mats often come in either dual or triple density foam inners to provide differing levels of support with the bottom or middle being the softer. With the higher density foam at the top this will prevent the climber's foot from sinking through the foam and either gaining impact on the ground or getting a foot stuck in the mat which would increase the chance of injury. Mats are often used to cover dangerous sections of the ground below a chosen climb such as protruding rocks or grass tufts.