This was early Red Phase of Basic Combat Training. This story does not involve Squirrel beyond him being in the room at the time. At this point we were being entrusted with the task of sending a canned letter home to our families from the battery commander. Apparently they didn't entrust us too much because our first-line DS was walking us through how to send a letter step-by-step (again, Squirrel was in the room, so I guess I understand). This is pretty much par for the course for Red Phase; only a couple days prior, our DSs had just taught us how to shower.

When our DS began his block of instruction on how to mail a letter, he held up the envelope for us all to see and said matter-o-factly,

"This is a window."

Us trainees simply sat there, patiently waiting to be presented with the wisdom our DS was imparting on us through this profound metephor.

Our DS's composure didn't change until he glanced briefly at the envelope, sighed, and simply said,

"Fuuuck me. Don't do drugs," then, raising the envelope again, said "This is an envelope."