Players can carry only a limited weight, and without a container only a maximum of 52 items plus gold and a loadstone. Thus, most games will involve the creation of a stash - a safe repository of objects.
Good stash location
Since monsters are quite capable of picking up and using any items they come across, it is best to stash items in a container. Using a heavy chest is more likely to stop a troll picking it up than a simple sack. No monsters are capable of looting any container, although gelatinous cubes can engulf any container except an ice box, destroying the container (but not its contents) immediately.
A good stash:
- is located in a convenient place. This is very often next to an altar, to tidy away all the items that numerous sacrifices will generate.
- is protected by (E)ngraving Elbereth into the floor beneath it. To burn Elbereth, use a wand of fire (uses a charge) or a wand of lightning (uses a charge and normally causes temporary blindness).
A very good stash:
- is a chest (as it is waterproof), near an altar, behind locked doors with Elbereth (E)ngraved into the ground around the entrances and the floor beneath the chest with boulders in front of them (if you have teleport control, that is).
Some players prefer a greater degree of organisation during long games, and so use several chests in their stashes. For long sessions of sacrificing at an altar, it can be useful to have one chest in which useful items are stored, and another into which junk can be cleared away. Players of extremely long games even have separate chests for each object type (potions, rings, wands, etc.).
The Castle or the Valley of the Dead are popular stash levels, as they both generate immense amounts of loot and have abundant chests. The Valley also has a temple, but it is unaligned. Another popular stash is the first level of Sokoban as it can be branchported to directly with the Eye of the Aethiopica, spawns relatively weak monsters, and is close to the Dungeons of Doom and the Gnomish Mines where there are many shops and altars.
Some players prefer to keep their stashes on levels which can leave bones files, so that if the unthinkable happens, they stand a chance of seeing their loot again, albeit through the eyes of a different character.
A chest or large box will suffice to protect your items from nearly all threats: No monster in the game can loot containers, and Elbereth underneath is enough to keep gelatinous cubes from eating it. A cursed item on top will keep your pet dragon from carrying it away.
Additional security measures beyond that are ineffectual, but paranoid players have been known to go several steps further. The easiest additional security measure is to place a boulder on top of your container. A chest with any sessile monster on it is incredibly secure, but inaccessible without killing or moving it (a tame blue jelly might work very well). An oilskin sack underwater is also perfectly secure, providing there are no water trolls on the level and you can get to dry land immediately after looting it.
Another good option is to use an ice box, which cannot be engulfed even by gelatinous cubes. Note that any item can be stored safely inside an ice box -- potions will not freeze, etc. Ice boxes are extremely rare, constituting 0.5% of all tools, and may need to be polypiled or wished for.
You can store items in a pit, and push a boulder on top of them. This makes the items totally inaccessible, except for you and monsters which are trying to flee by digging a hole in the floor. You will need a new boulder each time you want to cover your items after digging them up for retrieval. Organic items underground will rot, and will need to be placed in a container. The only container made out of a non-organic material is an ice box.
If your stash contains only junk, then perhaps it does not need security. That pile of cursed weapons and armor would not help those monsters much anyway. You might want to secure your junk if you plan to retrieve it later; you might come back for that potion of sickness and scroll of punishment when you have a pool, whether your plans involve making holy water or using a magic marker. Do not let some monster throw that potion at you!
In the early game, when you cannot yet secure your large box properly, the light shop in Minetown might be a reasonable location. Even if a digging monster does dig down the walls, they are repaired quickly.
Additional use of stashes - polypiling
As mentioned, you might have use for scrolls of punishment and so on once you have a wand of cancellation. If you have a wand of polymorph, polypiling is a great way to make use of otherwise useless magical junk.
The sortloot and menucolors patches can help you identify your stash. Both patches are installed on nethack.alt.org, thus many players do use them. When configured, the sortloot patch sorts the inventories of piles and containers, while the menucolors patch assigns colors to certain menu items. With these patches, you can list all your wands of fire together and flag as red all the cursed junk.