Creating a curtain requires a minimum level of skill that many powerful sorcerers allegedly do not possess; however, the difficulty of the technique varies depending on the complexity of the curtain, and as such, other less skilled sorcerers may be able to create less effective barriers. Skilled sorcerers may be able to implement specific conditions to their curtain.
The full method of deploying a curtain is unclear, but the user is required to utter the following phrase: "Emerge from the darkness, blacker than darkness. Purify that which is impure." (闇より出でて闇より黒くその穢れを禊ぎ祓え Yami yori idete yami yori kuroku sono kegare o misogiharae?).
Conditions can be used to increase or decrease a curtain's effectiveness or to specifically cater to a particular goal. For example, Juzo can create a barrier that only keeps out Satoru Gojo. These conditions typically can only be made regarding things that possess cursed energy. For example, a curtain cannot be created with the condition that cell phone reception is blocked; however, this may result as a side effect of its conditions. These conditions can be commissioned, implying that some level of preparation may be necessary for more complex curtains, but this is unclear.
The stronger the resistance inside the curtain (i.e. the stronger the curtain is in keeping people in), the weaker the resistance is to outside intrusion (i.e. the weaker the curtain is for people getting in). Barriers typically cannot be broken with brute force if they are strong enough. A barrier can be taken down when the sorcerer who created it is taken out.
Curtains may be created and imbued in objects, which then maintain the barrier until they are destroyed.