A dictionary of Confusable Phrases: More Than 10,000 Idioms and Collocations

door holder • doorkeeper
door holder —a device for holding a door open: Babyproof
your home by using door stops and door holders to make it
safer for your baby.
door keeper —a man who stands at the door of an establish-
ment and admits only those qualified to enter: We inquired
of the door-keeper, whereupon a woman came out to see us.
Note: 
The expression does not correlate in meaning with the
compound gatekeeper—
1
. a guard who tends a gate: The recep-
tionist finally gave the OK for the door to be opened by the
gatekeeper. 2. a person or group that controls access to smb. or
smth.: As our representative, they serve as our “gatekeeper” in
controlling the flood of information from the various media
organizations.
dot one’s i’s and cross one’s t’s • mind one’s p’s and
q’s
dot one’s i’s and cross one’s t’s —(also: dot the i’s and cross the
t’s) be very thorough; pay attention to small details: When
you do an investigation of somebody very prominent, make
sure you dot your i’s and cross your t’s.
mind one’s p’s and q’s —be careful of one’s actions and be-
havior; act and speak correctly: You’ll have to mind your p’s
and q’s if you want to be invited there again.
double as someone • double for someone
double as someone —(of an actor) act the part of two charac-
ters in the same play: Peck doubled as the hearty Yorkshireman
and the sinister Sir Mulberry Hawk in “Nicholas Nickleby.”
double for someone —act as a replacement for a person who
is ill, on holiday, etc.: I was just a stuntman on the film, but
I doubled for the head villain himself, Mr. Suzuki.
double bed • twin bed
double bed —a bed for two people: Each room sleeps two in
a double bed, and we can provide a camp bed at additional
cost.
twin bed —one of a matching pair of single beds: Students