When Wille was younger he always had several advent calendars. One with chocolate, one based on the TV advent calendar and one with 24 little gifts.
This year we've pared it down to the store bought chocolate one. I couldn't let the generic Santa image stay on it though so I pimped it a little bit. Bonus being this year's Christmas cat he's also featured on the calendar :)
I had planned to copy the calendar in a copy machine and then lay the copy on top of the printed image and cut the doors but I didn't get a chance to before the 1st so I made a template by laying a paper over the calendar and tracing where the doors are. I then laid the template on top of the image and cut through both with an exacto knife. After that I spray glued the back of the image and pasted it on the calendar. It's not 100 % accurate we noticed this morning when opening the first door but what the heck, its a disposable thing and will be tossed on the 24th anyway. I used an old ruler with letters and numbers and traced 1-24 with a silver pen on the doors.
Do you do Advent calendars where you live?

