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

be on the needle
—(sl.) be addicted to injectable drugs: My
brother’s on the needle, and I want to help him.
have pins and needles —have a pricking tingling sensation in
a limb: I have had pins and needles in my left hand for about
two weeks now.
be on the fiddle • fiddle about
be on the fiddle —(sl.) be involved in illicit money-making
activities: As it was day-time, everyone in the coffee bar was
on the dole or on the fiddle.
fiddle about—(coll.) mess about or waste time: I’ve been fid-
dling about for ages trying to get the windscreen washers to
work properly.
be on the hop • go on the hop
be on the hop —(coll.) 
1
. be very busy: I’d been on the hop
ever since morning, for being in love with Anita was a stren-
uous calling. 2. play truant; stay away from school, etc.: Re-
member that day I was on the hop from school? I went down
to the city that day…
go on the hop — = be on the hop 2: Ronan used to go “on the
hop” (skipping school) when he was a teenager.
Note: 
Neither expression correlates in meaning with the phrase
catch someone on the hop—(coll.) catch a person unprepared;
take smb. by surprise: You’ve caught me on the hop, I’m
afraid — give me five minutes to get ready.
be on the look-out for something • look out for
something
be on the look-out for something —be watchful wishing to
find or acquire smth.: Restaurant manager Jose Padilla is al-
ways on the look-out for something new for his customers.
look out for something —(also: watch out for something ) 
1
. be
on the alert for smth. harmful or dangerous: There were signs
everywhere warning people to look out for falling rocks. 2. =
be on the look-out for something: I’ve been looking out for a
new job for six months. 3. take care of smth.; protect smth.
from harm: When this young man is away from his home, I
look out for his property.
See also: outlook for something / outlook on something.