Corridor

In the Dungeons of Doom and Minetown, corridors are passageways connecting rooms. Not all corridors lead to rooms, and many have hidden sections (called a secret passage) which must are located by searching. Others may have boulders blocking your path. However even with boulders, it is never impossible to progress provided no scrolls of earth or unfortunate teleportation has occured.

Corridors are usually single file and always unlit. Telepathy, Warning or Infravision are helpful when walking in corridors.

Gehennom and Sokoban also have passageways and single file routes. However these are the level itself, rather than connecting rooms.

With the exception of death drops and the occasional scroll of teleportation, there is no loot in corridors but mercifully also no traps.

Strategy
The advantages of a corridor is that they are usually single file so you are less likely to be overwhelmed with enemies by numbers alone. The single file space also lines up enemies for convenient disposal by wands, spells or ranged attacks.

If you are overwhelmed by a long column of enemies you can displace your pet; switching places with it for a few turns to recuperate.

The disadvantages of a corridor is the darkness means you have difficuty locating enemies without Telepathy, Warning or Infravision. If you use an unidentified wand or potion, you will not identify it unless it is polymorph or a non-directional wand. This is a bigger problem for those roles relying on ranged attacks. A light source helps you avoid cockatrices, but also helps enemies find you.

Traipsing around corridors looking for loot and the downstairs burns your nutrition- in the first five levels this can force you to charge headlong in search of a fight in order find corpses to eat.

Cut corners to save time and get around faster. Corridors end when you find a door. If you are on an early level be sure it isn't a shop door before you kick it down.

Use a light source if you can spare it to avoid any awkward encounters. A light spell is particularly useful since it is permanent.

See if you can establish a circuit, a series of rooms and corridors you can cycle indefinitely to hold off and kill monsters which are as slow or slower but more powerful than you- by running in a circle you will recharge HP and Power over time. See hit and run

Creation of Corridors
You can create corridors yourself with the aid of a pick axe, dwarvish mattock, dig spell, wand of digging or polymorphing into a rock mole or umber hulk. If you find large amounts of rocks, gems or gold in a corridor this is a sign it has been dug by a monster. Always think of the possibility of a bones file character.

In particular, without a means of teleportation you need this ability to reach a Vault, a 2x2 room filled with gold.