First “real” life need for ninjaflex 
new blinding plugs for my sliding door
Those are weep holes. They allow condensation to escape from the and window frame.
Just molding, and voided warranties. And corroded metal between the panes
Nope these are facing out side and had original plugs that was disintegrating of old age and the hole give access to adjusting screw for the roller bearing for the sliding mechanism
And the metal is aluminum 
so corrosion is not that big of a deal
Gotca.