Bringing the carrier out only on vet day turns it into the signal for that trip, which is why it does not work. AAHA/AAFP notes that a reward-based positive association with the carrier can be taught and can make it easier to get to a veterinary visit.
Leaving the carrier open at home
The carrier can stay open and reachable at home, apart from clinic day.
Putting familiar scent and bedding inside
A familiar bed or scent can go inside.
Teaching voluntary entry with a reward
Voluntary entry is marked with a reward.
The step of closing the door
Closing the door comes after entering has become familiar.
Carrying the carrier for a short time
A short carry comes before the car.
Why forcing the cat in can set the process back
Forcing the cat in undoes the sequence built from voluntary entry.
A plan before the veterinary visit
The association is not built on the morning of the visit. The steps should already have been taken on earlier days.
