Create a PIN-only cashier
In the Dashboard go to Settings → Staff and press "Add with PIN". Enter a name (the name you use at the counter is fine, e.g. "Lan"), then the 6-digit PIN twice. Press "Add cashier".
This person cannot use the Dashboard, only the POS. In the staff list they show a "PIN only" label.
Pick a PIN that is hard to guess
A PIN is exactly 6 digits. Hensa refuses sequences like 123456, 111111 or other runs of consecutive digits. Birthdays and phone numbers are worth avoiding too – people at the shop may know them.
To change a PIN, go to Settings → POS devices → "Staff PINs" and press "Change PIN" on that person’s row. One PIN works on every POS device of the shop.
At the counter: pick your name, enter your PIN
The device shows "Who’s selling?" with everyone’s name. The cashier taps their name and enters their PIN. Someone without a PIN shows "No PIN yet" and can’t be tapped until a PIN is set in the Dashboard.
Stepping away for a moment? Press the lock button with your name at the top. Coming back, unlock with your own PIN; if someone else takes over, they press "Switch user" (needs a connection). The device also locks itself after a few idle minutes; the owner sets the minutes in "POS settings" (5 by default).
Five wrong tries: the PIN locks for a while
After 5 wrong tries the device says "Too many attempts. Locked until …" and "Ask a manager to unlock you in the Dashboard." The first lock lasts 15 minutes; another lock within a day lasts longer (30, then 60 minutes).
Everyone else keeps selling on that device meanwhile. To skip the wait, the owner or a manager opens Settings → POS devices → "Staff PINs": the locked person’s row says "Locked · … left" with an "Unlock" button, which unlocks them on every device. Only the owner can unlock the owner’s own PIN.
When someone leaves
Go to Settings → Staff, press "Edit" on their row and choose "Remove". They are signed out of every device and their PIN stops working; their sales history keeps their name.