A command in Nethack to toggle, aptly enough, two-weapon combat (no, it's neither an IRC channel nor an assassin version of Twoflower). It was first introduced in SLASH'EM, and was integrated into the "official" Nethack game in version 3.3.0. To use the technique, follow these steps:

  1. wield the one-handed, non-artifact weapon you want as your secondary weapon.

  2. Exchange weapons. This will leave your character fighting barehanded and designate the Step 1 weapon as "alternate; not wielded."

  3. wield the one-handed weapon you want as your primary weapon. This may be an artifact.

  4. Type "#tw" (NH will autocomplete #twoweapon) and press Enter. Your character will now attack with both weapons in a round.

"Two-weapon combat" is a separate skill from that of specific weapon classes, and uses a harsher table of to-hit and damage numbers than weapon skills do. Not only that, but since version 3.3.1, your character's skills in the individual weapons used figure in: the lower rating of the primary weapon's skill and two-weapon combat is used to calculate to-hit and damage penalties/bonuses (using the aforementioned table). This, plus the fixing of a few bugs in 3.3.0's #twoweapon code, makes #twoweapon a viable option for only classes that can really get good at it, such as Rogue and Samurai, or extremely high-level characters, whose base to-hit numbers are good enough to counterbalance the bad effects of low skill.

Interestingly enough, there is only one to-hit roll per #twoweapon attack; you will always either hit and damage with both weapons, or with none at all.