Angel banishing sigil

This sigil, once drawn in human blood, can banish an angel to heaven for a period of time. This sigil does no harm to the angels, it merely sends them back. It also doesn't harm the vessels they occupy. This is in a way a weakness for the angels. They can't stop it, once in use.

Its First appearance
This sigil was first shown in Heaven and Hell when the angels come to take Anna. She draws this symbol and banishes them for a while.

Now...
Once Sam and Dean gain this knowledge, they use it to defend themselves against the angels. Unfortunately, if they bring Castiel and its used, they lose Castiel's back-up.