Electric heat is the one part of reptile keeping that can go from fine to fatal while a house is quiet, which makes the heat-mat and thermostat briefing the most important conversation you will have with a house sitter. They do not need to become reptile keepers in an afternoon; they need to recognise each vivarium's normal at a glance, check it the same way every day, and know exactly which changes mean 'phone the owner now' rather than 'adjust something and hope'.
One card per vivarium, written for a non-keeper
Stick a card on the glass of every enclosure in the row. On it, in plain words: the animal's name and species, the warm-end reading the thermometer should show, the cool-end reading, the time the lights come on and off, when it was last fed and what it eats, and where its water bowl sits. Add a photograph of the thermostat showing the dial exactly where it must stay, and write under it in capitals that the dial is never to be turned — if the vivarium looks wrong, the answer is a phone call, not a hotter mat. A sitter managing a row of six enclosures cannot hold six sets of numbers in memory, and a card they can tick against beats a long document in a drawer every time.
Teach the two-minute daily check
Do one full round with the sitter before you leave and have them repeat it back. The round is the same each morning and evening: read the warm-end thermometer, read the cool-end thermometer, glance at the animal — where is it sitting, does it look as it did yesterday — check the water bowl, and tick the day's line on the log sheet. Show them the physical feel tests as backup: the glass over a working heat mat feels faintly warm through the substrate, never hot, and a thermostat's indicator light behaves the way you demonstrate. Explain that an animal sprawled as far from the heat as it can get, mouth open, is telling them the warm end is running away, while one pressed permanently over the mat and never moving may be in a vivarium that has gone cold. Two minutes per enclosure, twice a day, catches almost everything while it is still small.
The failure plan: power cuts, cold mats and hot glass
Agree the emergency script in advance and write it on the first card of the row. If a thermometer reads outside the card's range and stays there an hour later, if a heat mat is cold at both checks, if glass feels hot to a flat palm, or if the power goes out: the sitter phones you first, then the reptile vet whose number is on the card. For a power cut the instructions are simple — keep vivarium doors shut, lay spare blankets over the fronts to hold warmth, and touch nothing electrical. Show the sitter where the spare thermometers, the torch and the fuse box are, and leave one demonstration of a thermometer battery change. Everything the sitter needs lives in one place when you hand it over as a KinsLe Care Pass: each vivarium's routine, its normal readings and the emergency script sit together, clear and temporary, for exactly the days you are away.