This is used to make all footstep sounds in Counter-Strike: Source use the sound for concrete footsteps.
You drop this repo into the cstrike/custom/ folder for it to work.
More specifically, here's what the the file paths should look like.
steamapps/common/Counter-Strike Source/cstrike/custom/goodfootsteps/scripts/surfaceproperties.txt
steamapps/common/Counter-Strike Source/cstrike/custom/goodfootsteps/scripts/surfaceproperties_cs.txt