Walls are the basic unit of structure in a prison. They disallow players to pass into another area, and act as a good divider.
Walls can be destroyed by using chipping tools (to name a few, crowbar, Lightweight Pickaxe, flimsy shovel, sturdy shovel). As walls are chipped away, they lose durability. When the wall is down to low enough durability for your tool to break it, you will be required to have one empty inventory slot to make way for the wall block you will receive. Keep in mind that some special walls (ones that are covered in decorations or designs) are indestructible.
If the guards spot a broken wall in The Escapists 2, they will raise the Security Level by 3 stars. (in The Escapists, you'll be sent to Solitary!). Even worse, if they see you breaking a wall, then a lockdown will trigger and you will be sent to solitary. This can be avoided by replacing the wall block after you have finished using your passage, or by crafting a fake wall block as a removable replacement. An alternative for the Fake Wall Block is the poster, an item with infinite durability that can cover up wall damage (however it can be taken down by guards with a low opinion).
Walls are not the only barricades present in a prison. Some other types are as follows:
Cell bars cannot be destroyed in any way. They allow visibility, meaning other characters will be able to see you through them - watch for guards when you're in someone else's cell. These can be covered with Bed Sheets (one per tile of bars) to block visibility, but guards with low opinions of you will remove any hung bed sheets that they see.
Similar to cell bars, used in similar settings in some prisons of The Escapists 2. They appear to be glass windows, are unbreakable and allow visibility.