Wall

Walls are used to protect your settlement from attack by opponents. Walls, when filled with archers or crossbowmen, give ranged units a height advantage, effectively boosting their range, though not as much as gatehouses, towers, or keeps. Walls can be improved by adding crenelations, which helps defend archers and crossbowmen that are on the walls from attack. However, walls are vulnerable to siege equipment. Siege towers, catapults, trebuchets, and battering rams can break through your walls. Laddermen allow units to scale your walls, putting ranged units in danger, and allowing the enemy to take control of your walls. Assassins can also scale walls.

Types of walls

Stronghold has 3 types of walls:
Wooden Walls: Fairly simple walls made of wood, no troops can be placed atop.
Stone Walls: Stone walls that can be layered together for added strength, troops can be placed atop.
Crenelated Walls: Stone crenelations for stone walls that provide protection for troops on walls behind them, no troops can be placed atop.

Stronghold Crusader has 3 types of walls:
Low Walls: Inexpensive stone walls, troops can be placed atop.
Stone Walls: Stone walls that can be layered together for added strength, troops can be placed atop.
Crenelated Walls: Stone crenelations for stone walls that provide protection for troops on walls behind them, no troops can be placed atop.

Stronghold 2 has 4 types of walls:
Wooden Walls: Fairly simple walls made of wood, troops can be placed atop.
Stone Single Walls: Smallest stone walls with crenelations, troops can be placed atop.
Stone Double Walls: Same as Stone Single Walls, except thicker.
Stone Triple Walls: Same as Stone Double Walls, except even thicker.

Stronghold Legends has 3 types of walls:
Stone Single Walls: Smallest stone walls with crenelations, troops can be placed atop.
Stone Double Walls: Same as Stone Single Walls, except thicker.
Stone Triple Walls: Same as Stone Double Walls, except even thicker.