We drilled a hole through the floor and flush-mounted it. That also cures the "what to do with the cord stuck under the cinder block" problem, as well. If you don't have access under the coop floor, maybe some of those insulated staples, like the ones used to install land-line telephones, would work to anchor the cord in place. I also saw a youtube clip on using a metal cookie tin set-up, but you'd still have the cord issue. I didn't like that idea as much because I thought it would be too hot to the touch if the girls brushed up against it. I like the cinder block more for that reason, it's a softer warmth if they touch it. Hope this is helpful...
If the metal watering can you have is the type that you fill and place the cone top over it and birds drink from bottom? And your plan is to save money by not buying the heated base the company sells? You don't want to drill a hole or fit a cord in the top, to put any type of heater inside because it is vaccumm sealed with the top on. Same with the plastic ones that you fill, screw on the bottom while it is upside down and then right it. If the vaccume seal is not tight you will have a flood.
