Ladder

Ladders are wooden blocks used 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. Ladders can be jumped up to, 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 on which 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 are classified as a solid block, although this may not be apparent due to their thin nature. It is possible for a player to stand on the narrow top surface of the ladder, and damage can be incurred by a mob if it falls on the thin strip.

Ladders provide a way to safely cushion a player's impact after a 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. Once again, care must be taken to avoid landing on the narrow top surface of the ladder.

The ladder is one of the many blocks that is broken more quickly with a sword, but still incurs double damage on the sword.

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.

Since Beta 1.4, holding the sneak key whilst climbing a ladder grabs hold of the ladder, to prevent you falling off. However, when mining a block, the rate which a block is mined decreases while the player is holding onto a ladder. This effectively allows to break the "never dig straight down rule."

Before Beta 1.5, Ladders could be placed every other block, and still be ascendable. As of the 1.5 update, ladders must be placed on every vertical block you wish to ascend. When crafted, two are made, which means the same amount of sticks are used to ascend before and after Beta 1.5.

Crafting
As of Beta 1.5, this crafting recipe will give you 2 ladders instead of just one.

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.
 * If you place a bucket of water in a place occupied by a ladder with no other blocks next to it, the water will replace the ladder and you will not get the ladder back.
 * As of Beta 1.4, pressing the crouch key prevents the Player from moving down the ladder.
 * Pressing the crouch key on a ladder, and then walking forward has the same friction as walking on ice.
 * In Beta 1.5 instead of making one ladder you will make two.
 * As of Beta 1.5 you can't climb ladders that are placed every other block. This has no overall effect, as crafting ladders now gives 2, instead of 1.
 * A player stuck in Beta 1.5 due to a lack of ladders can still climb out using alternate ladders. Tutorial here.
 * If you stop yourself on a ladder and place a sign, you will still stay in midair without having to hold Shift.