Customers can register only if they are invited by gym owners, trainers, friends or through public gym profiles.
Your gym can offer services like private lessons or open tennis courts. You can specify the time which you like and reserve.
Caution: If your gym has cancellation policy in place and you are cancelling activity or service when it is already in place, they might charge you for your reservation.
You can reserve waiting list if the capacity is full or you can also be notified when a service of your desired time opens up. Simply by reserving that particular activity or service. You will be notified when a new spot opens up.