Instructables

Step 2: Push Down and Turn - 2

Don't put the thumbtack in the center. Put it close to the edge, but not right on the edge. If it's right on the edge, and slips between the caps, it sometimes won't catch the inner cap.

If the outer cap is really hard plastic it can sometimes be difficult to get the thumbtack through. You could just tap it in with a hammer or some other hard object, like that can of lima beans from 1978. On the hard ones, I've found just twisting the thumbtack a little, while putting pressure on it, will get it through pretty easily.

You could just put the thumbtack on the table with the point up. Turn the bottle over and push it straight down onto the tack. If the pressure isn't even, it's easy to bend the thumbtack. To keep the pressure even, just use three thumbtacks. Space them evenly around the edge and push the bottle down on them. Even if only one goes in, that's enough to lock the caps.

The only expense is a thumbtack, and what are those worth? Less than a penny? And it takes all of 15 seconds.
JoFrogger3 years ago
Thanks! I saw the wallet card about this at Maker Faire and picked up enough cards for my whole Parkinson's Disease support group. It's especially helpful because so many insurance companies now insist that you order drugs by mail, online -- no more asking your friendly neighborhood pharmacist to give you non-patient-proof caps in the first place.

Note that there's now another form of reversible/self-modifying cap: looks like the double lid type you disable with a thumbtack, but in this case you push down on the center of the top lid and it collapses onto the inner one. If you'd like an example for the next revision of this Instructable please let me know.