what does "portcullises" mean?

[Nathan]

English Language Tests, Intermediate level

ESL/EFL Test #293 "English Slang Idioms (15)", question 4

The police chief decided to pull out all the ......... on the investigation. He really needed to catch the dangerous, wanted criminal quickly.

(a) gates
(b) stops
(c) portcullises
(d) bars

English Language Tests, Intermediate level

ESL/EFL Test #293 "English Slang Idioms (15)", answer 4

The police chief decided to pull out all the stops on the investigation. He really needed to catch the dangerous, wanted criminal quickly.

Correct answer: (b) stops
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what mean by portcullises

Nathan

[Linda]

Hello,
The meaning is: "a grating of iron hung over the gateway of a fortified place and lowered between grooves to prevent passage."
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