People always ask if they can bring their TNR cats in a carrier to the vet clinic because they, the caretakers, want to be able to touch them or pet them and provide comfort to their pet.
However, it’s safer for the cat and the veterinary staff if the cat receives their first knock-out shot through the side of the trap. Using the trap, staff are able to corner in the cat so that it doesn’t wriggle about. If they wriggle too much, the shot may not penetrate the cat where it needs to or, worse, the needle might break-off from the syringe. Additionally, using this method, the cat is less likely to successfully scratch vet staff.
Here is a video of the process so you can see how it’s safer for both the cat and the vet staff to use the trap for the beginnings of the TNR process.