This is the TSBD front stairs from the first floor to the second floor.
View of the front door of TSBD from the inside
"Prayer Man" was standing on the other side of the glass from the heater
These arrows indicate one possible route Oswald could have taken from the First Floor Domino Lunchroom up the back stairs to the Second Floor Lunchroom.
If the man in the doorway "Prayer Man" is Oswald, then he must have gone up the front stairs to the Second Floor Lunchroom to get his coke, encounter Baker and Truly and then come back down the same way.