I was playing with this list of blender hotkey and i typed Alt-S but in edit mode. (Normaly in object mode it is “Clear size”)
This time in edit mode it gave me this “Shrink/Fatten” command. It works almost like size (S) but it is a little different but i cant really tell what it is for.
Alt-S only works on the outer edges of selected groups of vertices. Do it on a subdivided cube to see what I mean. Then select the vertices of only one half of the cube and do it again. Use it for modelling and RVK’s.