A method is provided for determining a characteristic of a flexible surface and determining a performance parameter of the flexible surface is disclosed. The method comprises providing a test device and pressing the test device into a flexible surface, measuring the pressures at the sensing points, and determining an envelopment parameter of the surface based on the pressures. The test device comprises a plurality of sensing points extending from a bottom of the test device upwardly along a side of the test device. A test indentor comprising a shell, wherein a least a portion of the shell is generally round in shape and has an exterior, with sensing points extending along the side of the shell, each sensing point is capable of detecting pressure at its location and an elastomeric material is on the exterior of the shell and adjacent the sensing points.