Hello, Instructibles gang…. I posted several questions related to “secret boxes” over the weekend. I got some feedback suggesting that the inquiries should have been combined, and that they didn’t include enough information to lead to worthwhile answers. The topics came to mind sort of haphazardly, so I do apologize for the scattershot nature of the original posts. As to the latter issue, “secrecy” was never the intention… rather, it was that this is all still in the “doodle” stage of planning, and I didn’t have a lot of details to give in the first place. Nonetheless, I’ll try to get a little more concrete - and combine the three questions in the process. I’m a letterboxer. Letterboxing stuff comes up now and then on Instructibles, but for those who are unfamiliar, it’s similar to geocaching (which seems to be more well-known), but with an added, artistic component. Whenever I see “secret boxes” in my regular Instructibles emails I think about whether the designs could be adapted for letterboxing purposes – either “on the trail” or at limited-time events and get-togethers. Naturally, I’ve been looking through my bookmarks and doing Instructibles searches, google searches, etc., but I’d appreciate if anybody might be willing to point me toward some of their favorite designs. I’m increasingly interested in creating boxes that are “hidden in plain sight” – not concealed, but rather “hidden” by virtue of the fact that they look like something else – such as a birdhouse or mailbox – and might in fact actually BE that something else, in addition to being a hiding place. I would welcome any suggestions that the community thinks might fit the bill. Here are some of the preliminary ideas I’ve been thinking about: 1) Folks hunting the box are told to take a 9v battery, with the snap-on wire leads, with them. When they get to the box they have to put the leads into two holes, where they and the battery complete a circuit. The current trips some sort of latch, allowing a door to be opened. Of course, the door would have to re-latch when closed again. 2) Something similar to #1 but a little more electronic. Hunters might be given a schematic of a simple Thing that they have to build and take with them. This would, essentially, be a key. I’ve already received an interesting suggestion involving RFID chips. I also got to thinking that a USB connection could be very discreet and easily hidden, and THAT got me thinking that the “key” could perhaps be something on a smartphone… data rather than hardware. I’ve got basically no background in electronics, but I’m fairly good at following directions…. 3) Pretty much any other contraption where some sort of hidden compartment would be created, which can be accessed through some sort of process that likely wouldn’t happen randomly or accidentally. (I know… could I be any more vague?) The boxes would likely be mounted to something solid - a tree, wall, post, etc. - but I imagine it could be that you take it down, do what you’ve gotta do, and then put it back. And they would most likely be exposed to the elements and would have to stand up to being out of doors. The size of the compartment is entirely flexible…no minimum or maximum dimensions. And, as stated, I’m a beginner when it comes to electronics – but I am more than willing to learn! I know what I’m trying to describe, but please let me know if I’m not doing well in communicating it to others. Like I said, I’m not trying to be secretive. It’s just that it’s still a very open-ended scheme – not many specifics – and I’m interested in hearing how different folks might approach it. Please shout if you have any thoughts or want more info.