The request is about safety in an unsupervised space, not about the tool itself.
What the kennel says
The things-to-know page asks you to remove a metal pinch-type collar before checking in. Metal can snag on chain link, and a dog caught on a fence can be hurt. The page adds that the kennel has these collars for dogs who need them and, upon request, will use one to walk a dog. If your dog depends on one for walks, tell the staff and they will talk through it.
What to put on instead
A flat buckle collar or a breakaway-style collar with your phone number on a tag is best in a run, and many owners also leave the tag on a flat collar only. Check the collar fits snugly but comfortably: two fingers should slide under it. Leave harnesses with metal clips at home if they dangle. Mark the collar, leash and harness with your dog's name. The kennel provides leashes, so you do not need to bring one.
Check-in routine
Because the kennel asks you to leave your dog in the car while checking in, plan to change the collar in the car before you hand the leash over. A staff member walks your dog in from the vehicle. This keeps parking-lot scuffles and escapes to a minimum. Keep the removed collar in the bag with your other belongings, which the staff will carry to the run.
Training and walks
If your dog pulls on walks, a front-clip harness or a head halter are alternatives to ask your trainer about. This glossary does not teach training. For the reasoning in more detail, read why we ask you to remove metal pinch (prong) collars at check-in and why remove a prong collar.
Related pages
See what to bring and indoor/outdoor run for how the runs and fencing are laid out.
Questions owners ask
Owners often wonder whether removing the collar will make the walk difficult. The staff are used to dogs of every size, and they can discuss your dog's habits at check-in. Others ask whether a head halter or harness is safe in a run. Dangling parts can catch, so remove anything that is not flat and snug. When in doubt, ask. The goal is a dog who arrives and leaves with no scrapes.