Java Edition:Invalid Ladder Placement

There were several methods to obtain invalid ladder placements, these allow for floating ladders or ladders on invalid blocks. Though obtained through older methods, newer methods to obtain invalid ladder placements mostly rely on Update Suppression.

Obtaining

Infdev 20100607

In Infdev 20100607, placing ladders off of the side of non-opaque blocks with a supporting block next to it can cause the ladder to be rendered invisible. If placed onto a slab that has two full blocks next to it, the ladder could be placed floating above the slab while invisible. The placement of the ladder depends on the direction of the last ladder the player placed, if no other ladders have been placed then using the slab method results in a full block ladder that is rendered invisible.

An invisible full block ladder.
An invisible ladder.

Block Replacement Bypass

Ladders can be placed invalidly using this method from Alpha v1.0.5 to Beta 1.4_01. This can be used to put ladders on transparent blocks and even air. Placing the ladder on air will cause it to render as invisible with only the hitbox being visible. The hitbox will change orientation to match the hitbox of the last ladder the player has looked directly at, and if no valid ladder has previously existed in the world, it will be a full block.

Transparent Blocks

From 17w18a (1.12 Snapshots) - 1.12-pre2 you could place ladders on glass, sea lanterns, glowstone, cauldron, leaves, ice, beacons and shulker boxes.^[1]

In 1.12-pre3 they tried to fix but but left in a method where you could place it as long as there was a valid block next to it^[2]

Stairs offset

From 17w18a (1.12 Snapshots) - 17w46a (1.13 Snapshots) placing a ladder on a invalid block with a stair facing towards it will place the ladder facing north.^[3]

Update Suppression

Needs testing.

Using update suppression, the ladder can be placed onto any block. The easiest method to do this is to use an Six Sided Piston and a redstone power source, however this only works until 1.8 due to the removal of 6 sided pistons. First, the player must update suppress the removal of the soil that the sugar cane is on, and after that, the player must update suppress once again with the placement of the block desired under the sugar cane. This method still works to 25w42a (present).