The PIN code is how Sherlock restricts its access only to its owner.
The first time a device is paired to a smartphone, a default 6-figures PIN code (123456) is required to finish the procedure. After this, you are asked to set a 6-figures personal PIN code.
In case you want to access your device from another smartphone or from a tablet, you need to insert your personal PIN code the first time you pair the device.
For this reason is strongly recommended to store your PIN code somewhere safe: in case you forget it and lose your smartphone, the device will be no longer serviceable.