- Too short is very untypical
- No space for the legs when moving, result : unsound movement
- Too long is undesireable
The back should be straight and strong with strong loins to be able to transfer drive from behind to have enough forward drive. Upward action leads to nothing and is useless for a working terrier and should not be strived for.
To some is may look spectacular, but it is complete and pure waste of energy.