Weep holes may be located both inside and outside the window in the bottom of the frame.
Image of weep holes sliding glass door.
These weep holes often get clogged with dirt and leaves requiring periodic cleaning.
They are under both the sliding and operating sash as well as the screen.
If the window is stacked there may be weep holes between the units.
Weep holes on sliders can be seen in the sill track.
We had one of our baths redone a few years ago but the apartment has been empty ever since as we were away from the country.
These weep holes are to drain the water in the track when the rain cascades down the glass.
A the time a frameless door was installed and we never thought about looking for weep holes on the track until now that we found your blog.
Some are on both the top and bottom but this is only so the door can be rotated during installation to reverse its operation.
Do not use abrasive or caustic solvents as they may damage your windows or patio doors.
Yes those are what we call weep holes they are necessary as you guessed to allow the water to drain out of the frame and into the shower.
Typically the water intrusion will occur through the bottom threshold and can be seen inside the home within the threshold itself but it will not reach the floor unless the weep holes are clogged.
I would suggest spraying a bleach solution into the holes from time to time to try to inhibit the mold growth in the framework.
To clean the weep holes use a small soft brush to clear the opening.
Sometimes an over zealous contractor may have accidentally caulked closed these holes during an effort to tuck point or provide external weather sealing.