Yep! Really useful, Bill!
...And if you don't have a knife, you can wear-off the end of the cap by scrubbing it along concrete. Rubbing on concrete also works for opening cans of tinned food in case your opener is lost or broken. You can smooth broken/torn fingernails the same way, and also thin out chain connector links if the one you were sold as fitting is just a smidge too wide to click shut (sometimes multiple widths are sold for a given chain, differing by 0.1mm or so; not all connect easily or at all, leading me to now check each and every one before departure).
All the best,
Dan.
