Abstract: The present invention relates to a device comprising a mat (1, 2), which has at least one through clearance (1.1) so that a remaining part constitutes an outer mat (1), at least one inner mat (2) being arranged in said at least one clearance (1.1) and said outer mat (1) having at least one first device-attributed, upper layer (1.4) provided with at least one non-rigid pile (1.5) of plastic in the form of artificial turf. Said inner mat (2) has at least one second device-attributed, upper layer (2.4) consisting of a material having a substantially smooth upperside and that is denser than the material of the first upper layer (1.4) of the outer mat (1). The present invention also relates to the use of the device.