The Check box form item is intended to enable or disable a certain option.
A check box can have two or three states.
Fig. 40. A check box
If a check box in a table column or a form is not available for editing, it appears shaded.
To toggle the value of a check box, click it. If you use the keyboard, first activate it using Tab or Shift + Tab, and then press the Spacebar.
If a check box has two states, you can also use the Plus Sign and Minus Sign keys to toggle it.