The Spider Wall Trap

The Spider Wall is a one room trap meant to slow down PCs in a dungeon, as well as deprive them of superflous goods such as ten foot poles, 100 foot lengths of rope, and sacks of iron spikes. The danger of the room is that the bottom is filled with four to six feet of a very unpleasant substance and falling into it is either extremely detrimental or outright lethal. Acid is a popular choice as it requires little maintenance and is self cleaning. Lava, pits of carnivorous sea bass or just a void that yawns down into the earth can also work well.

The room itself is generally 30 to 40 feet long, 20 feet from floor to ceiling, and about four to five feet wide, making it long, tall, and narrow. The floor of the room is recessed, leaving the caustic material a few inches from the PCs feet when they open the door into this room. The mode of traversing this trap is by pressing against the sides of the room with hands and feet, suspended by muscle strength. This does generally favor stronger characters, but said characters also tend to be more heavily laden with armor, weapons, and the afore mentioned laundry list of Adventuring supplies. Weaker or injured characters or NPCs might have to be carried across on the backs of a stronger characters, again at the cost of even more of their goods.

Variations
Sliding Walls - Sections of the walls rise or fall as PCs traverse across them, removing the ability for PCs to 'take their time' to improve their dice roll.

The Widening Room - When the door was opened, a hidden timer started and after a certain amount of time the two walls slide apart until they are 10 feet apart. After this, they slide back to their usual position, the movement action not resetting until the door into the room is opened again. The fluid level in the room drops, but enough remains to burn legs off at the ankles and remains lethal to anyone unlucky enough to fall into it.

A Hidden Path
If this trap is in a tomb or other verbotten area, it will serve as a deterent to anyone and everyone. In the case of the trap being a restriction against people who shouldnt be in the dungeon locale, there will be a way to bypass or neutralize the trap for those who are supposed to be in there. How else are the evil subterranean cultists supposed to carry on their evil deeds if they have to face the traps just like common PCs?

A Secret Password - By speaking a secret password, a magical effect is activated, causing one wall section to lever sideways and cover the acid, allowing the speaker to cross quickly with no danger. The lowered section only remains lowered for perhaps a minute, so there is no dawdling, and once the wall section starts to close, it will not stop, or re-open until it has closed completely. Get caught in the closing mechanism...SQUISH!