palpably rough surface texture the texturing means in the preferred embodiment is provided by rows of semi spherical raised dimples arranged in a grid pattern the areas between buttons preferably also have texturing means consisting of a plurality of rows of spaced dimples projecting upwardly there from to provide slip resistance in those areas e g for women in high heels and to improve maneuverability of wheelchairs to reduce the possibility of tripping the height of the buttons in one or more rows adjacent the side 107 of panel 100 is reduced in height and diameter relative to the height and diameter of buttons in subsequent rows so that there is a gradual increase in height and diameter thus in the preferred embodiment the buttons in the first row adjacent the side 107 of panel 100 are only about one third as high as the other buttons and the buttons in the second row are only about two thirds as high as the other buttons similarly the buttons in the first row have a diameter about 12 less than the other buttons and the buttons in the second row have a diameter about 3 less than the rest of the buttons the side 108 of the panel 100 adjacent the track in the embodiment shown is adapted to receive means to protect the panel 100 from damage in the embodiment shown side 108 of panel 100 has a first vertical wall section 116 extending from the top deck 103 a.