Air Layering With A Colander

The colander air-prunes the new roots, leading to a denser root system & hence, faster growth. If the plant you want to air-layer is in your possession, then use a colander type of pot. Avoid using an airtight plastic wrap or containers without holes on side and bottom. 

I feel people who do so, are ignorant of a basic concept shared here. Air-tight container makes sense only if the plant is not in your possession and hence cannot be watered often.

Air Layering Examples

Source : yenlingbonsai.com

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Also read - How Pot Design Affects Your Air-layered Cuttings 

Source : bonsaitonight.com / Jonas Dupuich

Trunk still has not been cut.  It goes further below.