The Plank is melee weapon which has very poor durability, but has a good ability to knock down zombies.
The Plank has a very heavy weapon (weight 3) and has a slow swing rate. It's main benefit is that it works well for pushing zombies away from the player and have an extremely long range in comparison to other weapons (the plank has range of 2, compared to the Baseball bat which has 1.5).
Extra wood planks can sometimes be found in crates in the warehouse or any other shed/storage building. Wooden planks can also be retrieved by smashing down doors and by converting logs into planks. The Plank cannot be repaired.
The Plank is also a multi-attack weapon, and can attack 2 zombies at once. It also can cause 5 door damage per swing, but no tree damage.
Non Weapon uses
A wooden plank is the staple fortification reserve in Project Zomboid. They are primarily used to barricade doors and windows or to fortify/create structures by making wall pieces, doors, door frames, window frames, crates, stairs, and barricades.
Planks used as barricades use their current health as part of the barricade. If a plank is at half durability and is nailed to a window/door, that durability is the strength of that piece of the barricade. Wooden planks can also be obtained by ripping away barricades on houses not occupied by the player (however planks may be damaged from previous attacks by zombies).
Wooden planks are also used to make bridges/flooring that can be crossed by both the player and zombies.
Planks have an additional use as a fuel for fires, and lasts for 4 hours if used this way.
Crafting (As Product)
To create brand new planks, cutting up logs with a saw is the primary way to do this.
A normal plank used as a weapon or for construction.
Crafting (As a weapon)
Planks can be turned into Nailed Planks which increase its damage output. As of Build 34.28, the extra nails do not lower the durability of the plank (unlike the baseball bat where adding nails gives a weapon penalty)