I Was just reading your comment/reply to @pooky-jax interpretation was required...
Rigid = Straight (usually a 20 foot to 30. Non combo.
Help me with "spanners". Is it turns? (round trips)
Steering Wheels?
My final guess would be...
What is a Wrench or Tool for $500 Alex?
Rigid = Non-articulated (i.e. no 5th wheel.
Spanner = Wrench.
We say wrench here too, but rarely.
This may help: https://www.nhvr.gov.au/road-access/mass-dimension-and-loading/general-mass-and-dimension-limits