A barricade is made by covering the area desired by the user with his pure mana, the larger the area the more mana it takes to cover it.

A barricade can easily break from the outside but the user who casted the barricade cannot harm his own barricade even after using the most dangerous techniques, this is the reason they are often used for protection. 

You can protect anyone by casting a barricade over them or casting a barricade on yourself and the enemy to protect others outside the barricade from harm. Many assassins use it for trapping their targets.

Breaking a barricade from the inside is only something the most advanced mana users can do for example, the head of the magic tower Issac Stallion.

The barricade shows the true color and nature of the caster's mana for example, Asher's barricade color was white and resembled soft serve vanilla ice cream.

The caster can detect if someone tries to break the barricade or if the barricade is broken.