Skip the wait. Not the cut.
A walk-in line your customers join from their phone. They scan a QR code at the door, get a ticket number, and get a text when it's their turn, so nobody has to sit in the shop waiting.
No app or password. Name, service, and phone number, and they're in line.
A heads-up when they're next, and another when a chair opens.
Barbers call the next customer, start the cut, and finish from any phone or tablet.
Show "Now serving" and "Up next" on any screen in the shop.