Tool textures are special textures which control how the map is compiled. They are found in zhlt.wad.

Name	Allowed as world	Allowed as entity	Casts shadows	Has lightmap	Cuts visleaves	Solid to cliphull 1	Solid to cliphull 2	Solid to cliphull 3	Solid to bullets	Info
`!cur_0`*	Yes	No	Yes	No	Yes	No	No	No	No	Acts like `CONTENTWATER` and `func_pushable` with a speed of 2048 units/s in +X. This texture is always fullbright.
`!cur_180`*	Yes	No	Yes	No	Yes	No	No	No	No	Acts like `CONTENTWATER` and `func_pushable` with a speed of 2048 units/s in -X. This texture is always fullbright.
`!cur_270`*	Yes	No	Yes	No	Yes	No	No	No	No	Acts like `CONTENTWATER` and `func_pushable` with a speed of 2048 units/s in -Y. This texture is always fullbright.
`!cur_90`*	Yes	No	Yes	No	Yes	No	No	No	No	Acts like `CONTENTWATER` and `func_pushable` with a speed of 2048 units/s in +Y. This texture is always fullbright.
`!cur_dwn`*	Yes	No	Yes	No	Yes	No	No	No	No	Acts like `CONTENTWATER` and `func_pushable` with a speed of 2048 units/s in -Z. This texture is always fullbright.
`!cur_up`*	Yes	No	Yes	No	Yes	No	No	No	No	Acts like `CONTENTWATER` and `func_pushable` with a speed of 2048 units/s in +Z. This texture is always fullbright.
`AAATRIGGER`	Yes	Yes	Yes	No	Yes	Yes	Yes	Yes	Yes	Identical to `NULL`, but shouldn't be used on world brushes as it may cause bugs. Useful for differentiating entities in the editor.
`BEVEL`	Yes	Yes	Yes	No	No	No	Yes	No	Yes
`BEVELHINT`**	Yes	Yes	Yes	No	No	No	Yes	No	Yes	Acts like `SOLIDHINT` and `BEVEL`. Eliminates unnecessary face subdivision and bevels clipnodes at the same time. Useful on complex shapes such as terrain, spiral staircase clipping, etc.
`black_HIDDEN`	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Identical to `NULL`, but has a lightmap. Brushes with this texture can cast shadows. This texture will not render as black except in Sven Co-op.
`BOUNDINGBOX`	No	Yes	No	No	No	No	No	No	No	Acts like `ORIGIN`, but can be used to define a bounding box for an entity. Useful if you have a lot of complex, off-grid geometry and need a bounding box which is snapped to the grid.
`CLIP`	Yes	Yes	No	No	No	Yes	Yes	Yes	No	Creates clipnodes on all three cliphulls.
`CLIPBEVEL`	Yes	Yes	No	No	No	No	No	Yes	No	Acts like `BEVEL` but for clipnodes.
`CLIPBEVELBRUSH`	Yes	Yes	No	No	No	No	No	Yes	No	Acts like `CLIPBEVEL`, but affects every single face.
`CLIPHULL1`	Yes	Yes	No	No	No	Yes	No	No	No	Creates clipnodes on hull 1, used by standing players.
`CLIPHULL2`	Yes	Yes	No	No	No	No	Yes	No	No	Creates clipnodes on hull 2, used by large monsters (apache, gargantua, gonarch, etc).
`CLIPHULL3`	Yes	Yes	No	No	No	No	No	Yes	No	Creates clipnodes on hull 3, used by crouching players.
`CONTENTEMPTY`	Yes	Yes	No	No	No	No	No	No	No	Removes collision from a brush and marks a brush as an empty volume.
`CONTENTWATER`	Yes	Yes	Yes	No	Yes	No	No	No	Yes	Marks the brush as a water volume that will not render anything outside of it. It also removes collision from a brush and mirrors the faces inside out. When an entity, it is an empty volume with mirrored faces.
`HINT`	Yes	Yes	No	No	Yes	No	No	No	No	Faces with this texture will split visleaves, allowing you to optimize what parts of the map are visible. Other faces of the brush should be textured with `SKIP`.
`NOCLIP`	Yes	Yes	Yes	No	Yes	No	No	No	Yes	Acts like `NULL`, but no cliphulls are generated. Similar to the `zhlt_noclip` keyvalue in entities.
`NULL`	Yes	Yes	Yes	No	Yes	Yes	Yes	Yes	Yes	Removes the face of a brush it's applied to, however clipnodes are still generated.
`ORIGIN`	No	Yes	No	No	No	No	No	No	No	Brushes with this texture will act as the point of origin for entities.
`SKIP`	Yes	Yes	No	No	No	No	No	No	No	Ignores the face of a brush it's applied to. Should not be used on world geometry except with `HINT`, as it may cause bugs.
`sky`	Yes	No	No	No	Yes	Yes	Yes	Yes	Yes	Renders the skybox on faces with this texture, and emits light if all faces of a brush are textured with `SKY` and you have a `light_environment` or `light_spot` entity.
`SOLIDHINT`	Yes	Yes	Yes	No	Yes	Yes	Yes	Yes	Yes	Used to eliminate unnecessary face subdivision, especially on complex shapes such as terrain.
`SPLITFACE`*	Yes	Yes	No	No	No	No	No	No	No
`translucent`	Yes	No	Yes	Yes	Yes	No	No	No	No	Removes clipnodes and mirrors the brush faces inside out.

*This tool texture functions normally in Vluzacn's ZHLT v34, but is missing from zhlt.wad
**This tool texture exists only in SDHLT v0.1

1. BEVEL

This texture acts like NULL, however it changes the clipnode of a brush in a way that any player approaching the brush will not be collide with the brush until their origin reaches the plane that the BEVEL face lies on. It can be used to eliminate exterior corner clipping bugs, and any remaining clipping bugs that the -cliptype precise CSG parameter may miss.

1.1. BEVEL vs NULL

Replacing NULL with BEVEL in your entire map is not always a good idea. While it reduces clipnodes, it can also cause bad collision where players fall through floors, can walk inside walls, get stuck in an edge where two walls meet, etc.

2. SPLITFACE

Brushes with this texture will subdivide faces they touch along their edges, similarly to zhlt_chopdown. Imagine your SPLITFACE brush as a "cookie cutter" that cuts into any walls it touches.

Here's how it looks like in-game with gl_wireframe 1.

SPLITFACE is useful for fixing lighting bugs where shadows "leak" out from behind opaque entities. In the following example, the big crate is a func_breakable entity with the Light Flags keyvalue set to Opaque (Blocks Light).

The shadows won't be calculated properly unless we split the faces behind and below the crate along the dotted line.

Since you can't use zhlt_chopdown on a brush entity, this will have to be done by either creating a SPLITFACE brush along the dotted line. Any of the following methods will work. My preferred method is the second one, where I make a copy of the crate and texture it with SPLITFACE, to make it act like zhlt_chopdown.