Scaffolding

Scaffolding is a special placeable item that can be directly placed or removed by the player and allows dwarfs to pass and climb through them, stand still and work over them.

Game description
"Dwarves can climb on scaffolds to do work up high. You can instantly install and remove scaffolding when you wish."

- Craft the World Inventory

Behavior
Scaffolding are quite similar to ladders regarding their transportation functions, but unlike ladders, scaffolds fall if the block under them is removed/dug. So, the player can lose as many scaffolds he/she places over the lava.

The game prioritizes removing scaffolding over interacting with any other object on the same block (except when right-clicking). This makes it difficult to for example select a dwarf if he's climbing or walking on the scaffolding.

Multiplayer
Scaffolding cannot be used in biomes, that were the first environment for multiplayer matches. This lack is fixed in multiplayer games created with the Dig with Friends DLC, where the scaffods of each player have little ribbons with their respective colors. Each player can interact only with their own scaffolding.