Ladder

Ladders are wooden block decals for climbing walls either vertically or horizontally, and were introduced to the game in Infdev. They are created by arranging an H-shape of 7 sticks on a crafting table and can only be placed on the sides of other blocks. Players who want to conserve wood can place ladders every other block and still successfully climb them vertically; they can also be jumped onto, allowing the bottom of a ladder to be two blocks off the ground and still be accessible.

Like torches, a ladder occupies one block from the side it is placed and cannot be placed on glass. Unlike torches, however, they resist water and will create an air pocket. They also resist lava, and can be used instead of glass to let lava light shine through a ceiling. If you place a ladder in lava or water just on the ground not near a wall, it will still have an air pocket but will be invisible, still there though, thus the invisible block.

Ladders provide a way to safely travel downward at maximum velocity (free fall). Upon entering a ladder's area of effect, the player's speed is reduced instantly to normal ladder descent speed and no damage is taken. However, care must be taken to avoid landing on the narrow top surface of the ladder.

Ladders are one of the many blocks that are broken more quickly with a sword, but still have double damage on the sword.

Like the player, Pigs, Sheep, Cows, Chickens, Spiders, Creepers, Slimes and Zombies can climb ladders. Skeletons are unable to climb ladders, but will shoot up if you are within firing range. It is unverified whether or not other mobs (Namely zombie pigmen) can climb ladders, however it is assumed they can since all other mobs are able to.

Spiders can be blocked from climbing a wall by placing a ladder at the top edge of the wall. This is because the ladder is technically a block and it sticks out from the wall enough to hinder the spider's climbing.

Due to the South/West Rule, Ladders can be used to create a Water Ladder, which allow the player to ascend quicker. Signs can also be used.

Trivia

 * It takes approximately 52 seconds to travel from bedrock to the roof of the sky on ladders.
 * Placing ladders on snow layers make the ladder invisible but they still act as if you placed them normally.
 * You don't technically climb a ladder, you just walk into one and then you'll rise. This is explains how creepers can climb ladders.

Gallery
Leitern Drabina