If the object endpoints do not overlap, a dialog box will appear stating "Crosshatch boundary is not completely closed. Proceeding may produce an incorrect crosshatch." If you click OK, Claris CAD will try to create the crosshatch. If it is unable to produce any crosshatch it will beep.
TIP: To see if endpoints overlap sufficiently, select one of the objects, and from the Edit Menu, pick "Select Adjoining". Adjoining objects become selected.