PrF UG inst entry field boolean
From Protege Wiki
The Boolean Fields
When an instance is created for a class with a slot of Boolean value type, the entry field corresponding to the slot is a Boolean field, and contains a value which is either true or false.
An instance with a Boolean field with Single cardinality displays as a checkbox. To set or change the value for a Boolean/single slot, click in the box to add or remove the checkmark.
For example, the Personals_Ad class contains the Boolean slot Urgent; the Silly instance of Personals_Ad is not Urgent, while the M137 instance is: