Ever wonder when the last time you changed your HVAC filters was? Using a bright colored index card, I write the years, with corresponding months, leaving room for my date I changed the filters for the next three years. I make one for each filter location. I attach it to the wall with two hook and latch dots. I also attach a pen this way, so it's always at the ready!
And now I have two checklists for three years: 2021, 2022, and 2023. You can use a white index card and double sided tape to make it very easy. Keeps your unit running more efficiently!