Pressure Seal - The pressure seal process uses pressure applied to the mailer in an area where special cohesive sealant has been applied. The sealant is applied in a specific pattern and location on both sides of the mailer so that when it is folded the  areas of sealant come in contact with each other. Pressure is then applied in these areas causing the cohesive sealant to form a bond. The sealant is applied so that all edges are sealed.

 
Cold Glue - Cold glue is applied by a glue folder. The glue folder applies a glue line on the left and right edges and spot glues across the top or bottom, whichever is the open edge. It then perforates the mailer along three edges. When completed, the mailer is sealed on all edges.

 
Pressure Sensitive Tape - A strip of pressure sensitive tape could be used along the closure edge of a mailer to seal it. The PS tape closure would leave the left and right edges unsealed.

Remoistenable Glue - A remoistenable glue is applied to the mailer when it is manufactured. Like the cohesive sealant, it is applied in specific locations on both side of the mailer. when the mailer runs through the folder/sealer, water is applied to the glue areas. The mailer is then folded and sealed. The remoistenable glue is applied so that all edges are sealed.

 
Remoistenable Glue Strip - When the mailer is manufactured, a strip of glue is applied to one of the edges parallel to the fold of the mailer. The glue is moistened to seal the mailer once it is ready to send. This closure would leave the left and right edges unsealed. The mailer may also have an integrated envelope. An integrated envelope would be glued at the edges and have a remoistenable glue strip applied to the flap area.