i have a temp gun so it eliminates the need for any kind of cords inside my snakes cage therefore avoiding the risk of the snake getting tangled in them.
just like the others said though, the thermostat probe needs to be placed between the u.t.h & the underside of the cage so its able to sense when the u.t.h has reached the temp the thermostat is set to. it's an on/off sort of thing (it turns the u.t.h off when it reaches the desired temp setting & on again when it goes lower then the temp setting, therefore keeping the temps where you have them set.)
the thing with the repti-temp 500r though is because it is not digital, the overall room temp will effect how much & fast the u.t.h heats up so the thermostat will have to be constantly adjusted to keep the u.t.h under control so the temps will have to be checked frequently.
it is definitely NOT a "set & forget it" deal.