After the sandwich of the two panes and gasket has been layed down in the inner sash, it's time to add the breather. The breather has one sharp tube that can be pushed through the gasket into the air-gap between the two panes. The other tube below it is blunt and is hard to push through the gasket material. I use an appropriately sized drill to drill a guide hole for it. When done this tube exits the gasket centered between the inner pane and the inner sash. Visible to the left of the breather is a small screwed-on plate which prevents the breather from moving back out of the gasket. To make installing the breather possible it's necessary to locate the gasket joint off center. I make sure to have it offset by several inches.