Crossword Genius

Geometrical instruments used for making walking aids (9)

Ross

I believe the answer is:

callipers

I'm a little stuck... Click here to teach me more about this clue!

'geometrical instruments' is the definition.
'callipers' can be an answer for 'instruments' (calliper is a kind of instrument). I am unsure of the 'geometrical' bit.

I can't explain the rest of the clue.

Can you help me to learn more?

(Other definitions for callipers that I've seen before include "measuring instrument" , "They can't work without legs" .)

I've seen this clue in The Irish Independent.
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