$decal

$decal is a material shader parameter available in all Source games. It offsets any faces assigned the material by a minuscule amount along its surface normal, preventing z-fighting with coplanar faces. This makes it suitable for decals.

When used on "proper" decals/overlays, as well as brushes and displacements, it disables depth writing^[Clarify], causing the surface's depth to be inherited from underlying geometry. This can cause a $decal material to look weird when used on a brush/displacement that isn't coplanar or nearly coplanar to a non-$decal brush. If the geometry *is* coplanar, however, this command can be useful for making "pseudo-decals", to enable effects that normal decal and overlay entities don't support, such as normal mapping.

Confirm:Does the disabled depth writing also occur for models, or does it just cause the offset there?