40d:Hatch cover

A Hatch cover is a circular covering for a hole in the ground, which is effectively a vertical door. It is classed as furniture and can be built from either rock, wood, metal or glass. When closed, hatches have the symbol ¢, and when open they look like empty space.

Hatch settings

There are three options one can specify on a door from the q menu:

• l Forbid/Permit Passage
  • A hatch set to Forbidden is impassable to any dwarves in the game. A hatch cannot be set Forbidden if it is open. Invading thieves may lock-pick and bypass a Forbidden hatch.
• o Keep Tightly Closed/Make Pet-Passable
  • A hatch that is pet-passable allows through traffic of pets. A pet can still pass through a hatch that is tightly closed if it does so while it is being held open by an object or dwarf.
• s Set as Internal/External
  • A hatch set to external functions as a floor? when defining boundaries of a room such as a bedroom. A hatch set to internal allows the room boundaries to pour over.

Building Hatches

After constructing a hatch at any of the above workshops, they must be "built" (placed) like all other furniture. Hatches can be built on any free floor tile, over empty space, or on top of down-staircases (or up/down staircases, or even up-staircases, although that last option won't do anything useful). Hatches cannot be placed on the same tile as most other constructions, including all furniture and traps. However, they can be placed on "rough-hewn wall" tiles, which somehow leaves the wall intact!

To be used effectively, a hatch should either be placed above a downstair (or in an up/down stair) where, like a door, it will impede liquid flow while still allowing access; or alternatively it can be linked up to a lever (and probably placed above a channel, or lava, or below a river etc), which when pulled will temporarily open the hatch, allowing whatever is above to fall down below.

Like grates, hatches placed on top of floor tiles are purely decorative. Placing a hatch cover does not automatically dig out anything under the hatch.

Water which has a hatch on top of it can still be used as a water source and for fishing.

Hatches over empty space can be safely walked on and even driven over by caravans (They do need to be next to a wall or floor for support, however, but they can't even be built if that condition isn't met - and supports on the level below don't do any good ^[Verify]).

You also can't build a hatch in a stockpile area. Which is really too bad, because otherwise you could put a stairway in every stockpile tile without fear of miasma.

Floor Hatch

A Floor Hatch is door based on the Z-axis. When you create a stairway between two floors (both an upwards staircase on the lower floor and a downwards staircase on the upper floor) the Floor Hatch, when put on the upper floor staircase, acts like a door. If you lock it, the dwarves will not use that staircase. A closed floor hatch will block the passage of fluids onto the lower floor, and will stop falling creatures. They can also be used on ramps. Floor hatches can also be placed on open space, provided they have support.

Uses

Floor Hatches could possibly have another use:

• Trap doors when hooked to pressure plates?
• For use over pits and ponds?
• Preventing water and magma from flowing down stairs or ramps - useful for aquifer levels
• Last minute defense for an invasion? (Mainly for fortress built right into the ground)
• Cover for stockpile stashes hidden underground?

Testing

Testing shows that in a nutshell:

• They work just like doors. Only on the Z-axis.
• The hatch will be flashing if placed over stairs.
• A dwarf falling down a multiple floor stairway will be stopped by a closed floor hatch.
• Hatches can be linked to levers to function like a "vertical" floodgate without blocking liquid accumulating on the surface above - for example they can be used as emergency drains for pools of water - or magma, if made of magma-safe materials.

More testing is required.

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