French door
archway
back door
barway
beginning
border line
bound
boundary
boundary condition
boundary line
bourn
break boundary
breakoff point
brink
bulkhead
carriage entrance
ceiling
cellar door
cellarway
circumscription
commencement
compass
confine
cutoff
cutoff point
dawn
deadline
delimitation
determinant
division line
door
doorjamb
doorpost
doorsill
doorstep
doorstone
doorway
edge
end
entrance
entrance hall
entranceway
entry
entryway
extremity
finish
floor
foyer
first
get-go
kickoff
offset
outset
showtime
sill
start
starting time
thresholding
thresholds
thresholdless
thresholdlike
circuit
criterion
depth
dimension
frequency
gate
glimpse
input
level
limit
parameter
peak
phase
range
requirement
stair
verge