One reason the acclimation period is used is to accustom the wolves to their new surroundings and hopefully dampen their strong homing instinct so they won't try to head back to where they came from as soon as they are free.
Another reason for the acclimation period is to get the wolves used to the taste of the food they'll find in their new homes. At Yellowstone the gray wolves were fed road-killed elk and deer. The red wolves at Alligator River were fed road-killed deer, opossum, raccoon, nutria, squirrel, and rabbit.
The acclimation pens are made of panels of heavy-gauge chain-link fencing. The fence is 8 feet tall with an overhang to prevent the wolves from jumping out. Inside the perimeter is a chain link "digging barrier" to stop the wolves from digging their way to freedom before they have completed their acclimation. The pens at Alligator River and the Great Smokys are 50 x 50 feet. The pens at Yellowstone for the gray wolves are nearly an acre in size.
During the acclimation, human contact with the wolves is kept to a minimum. A wolf's best defense in the wild is stay away from people. Every attempt is made to keep the wolves' natural fear of human beings intact.
Biologists visit the pens a couple times a week to deliver the food and check on the wolves. A few days before they are released the wolves are caught and given their final physical examination by the veterinarian. They are weighed, inoculated against disease, and if needed, equipped with new radio collars.
On a day of the release a biologist walks up to the pen, opens the door, and walks away. The rest of the story is up to the wolves...