Not familiar with the 'Hold Heet' brand of glue pot, but a good way to
figure this out is if the heating element looks like the small diameter
wires in the toaster then do not add water.

I'm assuming the glue pot can be removed so you can see the element.
The easy way to check is take the pot out, turn the thermostat up all
the way, plug in unit and see if the wires glow red-orange.  If this
is the case then it is _dry only!_

If the heating elements are large diameter, generally gray in color,
they are encased in aluminium.  The water-tight aluminium can will
have a white scum on it from cooking the water out of the pot from use.
Hope this helps.

Glen R. Perye Jr.