Testing should be carried out in accordance with the relevant standard or guidelines. However, where no standard or guidelines exist, we suggest the following procedure.
This section covers the procedures for the measurement of slip resistance of flooring materials in the laboratory. Allowance for surface texture is made by taking measurements in three different directions. This procedure may not be appropriate for materials, profiled or uneven flooring materials present a problem and in some cases quite unrealistic friction values may be recorded.
In some instances, where the surface roughness of the flooring material is below 15µm Rz, a true reading of the wet slip resistance may not be obtained because the surface roughness of the Four S Rubber Slider is greater than that of the flooring material and inhibits the formation of a water film between the Rubber Slider and the flooring material. The main parameters of consideration are the friction in wet or contaminated conditions between the Rubber Slider and the floor surface and the roughness of the flooring material. A truer reading may be obtained by preparing the Four S Rubber Slider on 3µm pink lapping film as described in the Skid Tester Manual. 
As used by FIFA for tests on grass and astro turf
In all cases it is imperative that proper contact between the working edge of the Rubber Slider and the test surface is maintained throughout the contact length.
Two types of Rubber Slider are available for Laboratory testing of flooring surfaces using the Main Graduated Scale. The TRL (Transport Research Laboratory), Rubber Slider is commonly used on surfaces where the general roughness is greater than that normally found with internal flooring situations. For testing most internal flooring materials, those with a roughness of less than 15µm Rz, then it is customary to use the Four S (Standard Simulated Shoe Sole) Rubber Slider.