pesachim 85

what is inside is stripped to the bone.

but what's outside remains outside.

except for prayer.
prayers can fly through iron walls

(if a limb of the pesach offering goes outside of the boundary, the part inside is stripped of the meat to the bone, and the outside bit untouched. the talmud then discusses if the thresholds, the doorway and windows are considered inside or outside. to be included in the communal prayer one ought to be inside, and not at the doorway. but R. Yehoshua ben Levi stated that even an iron barrier does not come between people in prayer and God.)

gmar tov. whichever side of the doorway you position yourselves this Yom Kippur.

eruvin 101

what is a door?

the man of thorns stands guard at the edge, at the threshold, and protects. and sends the enemy to the gates of hell.

(this page discusses the definition of a door, when is a partition something that closes a gap in a wall, and when is it a door. hinges? appearance? distance from the floor? and does the door belong to the private or public domain, and how to use a key to go from these two domains without doing any prohibited carrying between domains.
one of the partitions that is discussed as a door is a bundle of thorns. this leads to interpreting the verse from Micah about a man of thorns being a protection and sending enemies to gehenna, hell)

eruvin 11

some doorways allow carrying & freedom of movement.
and some don't.
& locking out opinions that don't fit your definitions

(R. Sheshet instructed R. Gadda to destroy a doorway in the Exilarch's house that was allowed by R. Nachman. R. Gadda ended up in prison and R. Sheshet stood at the prison gates, calling him to free him. R Sheshet did not want a particular discussion about mezuzah on an arched doorway to be taught to the Exilarch's household, as it disagreed with his opinion)

eruvin 3

look up and think BIG
some numbers are not exact , they are rough, like the edges of a bird's nest.

and measurements depend on having an open hand.
or a clenched fist.

(in the discussion about the maximum height of a doorway, the cornice in the temple is described as having an eye-catching bird's nest design. and height is 100 cubits. except the number 100 is not exact, it is an exaggeration and just means something big. this lack of exact definition is also found in the discussion of what is a cubit. 5 or 6 hand-breaths? or always 6 hand-breaths. and sometimes the hand is open with fingers spread out, and sometimes it is closed. there is no one singular definition of a cubit. depends on context)

eruvin 2

what makes a doorway THE doorway?

(debate about the maximum width of the entrance to an alleyway is a debate about which entrance to the temple/tabernacle is definitive. the one to the hechel, the inner sanctum, to the alum, the main hallway, or the extra special king's entrance. what do you have to pass through to be on the inside?)