If someone is interested in buying an Apple Watch, they better have one on reservation or have one pre-ordered.

Reports say that without a reservation or having the watch pre-ordered, it will be hard to find the device as a walk-in customer, 9to5Mac reports.

One source at an Apple store said, "we're told to treat launch day as if there will be no walk-in stock."

There still could be some available without a reservation but getting the exact model that a customer wants could be difficult.

The availability of the watch will depend on the location, including the store's state and country. China is expected to have more stock of the device. The Apple Watch's availability in the United States will be focused on those with reservations. The watch will also be available in Canada, France, Japan, Germany and the U.K. on launch day.

If Apple can increase the supply of Apple Watch devices available the company might be able to meet the growing demand, but they do not have much time. Apple will start selling the Apple Watch at Apple Store locations April 24.

Starting April 10, customers interested in the Apple Watch can visit Apple Store locations to try on either the Apple Watch Sport or the stainless steel Apple Watch. They will be given 15 minutes to try on the models and appointments are not required.

Sources say that appointments for the 18-karat Apple Watch Edition could take up to 30 minutes, but one source said, "it's not like we'll kick out the Sport and stainless steel customers if they're taking too long." Only the highest traffic flagship stores will have the 18-karat gold Apple Watch.

Customers will also be able to pre-order the Apple Watch online from April 10. Deliveries of the watch will occur beginning on April 24, which is the launch day of the watch in stores. Unlike new iPhone and iPad launches in the past, pre-ordering the device for in-store pickup will not be immediately available. That could change as more quantities of the device is made available.