Skip textures are applied to the surfaces on brushes with Hint textures that should not be used to break up visleafs (or leafs in short). Usually, a brush used for hinting has a hint texture on one or two surfaces and skip textures on the rest. Skip textures do nothing more than make the tools skip the brushsides they are applied to; they owe this property to the %compileskip .VMT parameter. For the usage of hints, see the hint brush section.
Enveloping a group of precisely placed objects, inside a normal brush on par with a larger grid size, and then selecting these components together with the brush, will help preserve the exact grid positions of the components when the group is moved according to the gridsize of the enveloping brush. As this brush is merely a tool for the design phase, covering the enveloping brush in Skip textures will prevent this brush from being processed into the map. (For detailed instructions, see the prefab article.)