It was observed by someone about a year and a quarter ago that I was in need of a penlight, a small flashlight about the size of a pen. And so I was presented with a penlight. It takes one triple A battery, and fits neatly into the top of a trouser pocket (if one wears trousers with reasonable, functional pockets.) It is good for glancing into cylinders (Yep, really are that gunky. Hoppes #9 here we come), for finding small objects in dim light, for reading menus in dim light. You know, flashlight things.
It is also spectacular for use in museums and castles. Those dimly-lit, irregular stairs? Are now decently lit for someone who has mild mobility problems. You can peer into dark chambers to see if there is anything of interest. You can get a better look at artifacts in display cases if you angle the flashlight properly, and are discreet. (If the information talks about how light-sensitive the colors are, well, don’t spotlight the item.) It brings out amazing detail in Bronze Age, Iron Age, and Saxon jewelry and brooches. And in the Lewis Chessmen.

And then there’s the fascinating baptismal font, commissioned by a MacDonald clan chief. In the 1500s. OK, remember, 1500s. Renaissance.

So, why not use the light on your cell-phone, if you carry one? Well, some places are still no-phone zones, like Rosslyn Chapel and other churches. Some museums are no-camera zones as well. A pen-light doesn’t attract the ire of docents. A pen-light doesn’t drain batteries, and it can give far more focused light than the phone flashlight does. It can also be discreetly concealed in the palm of even a small hand. And if you drop the penlight on stone steps, and it bounces a meter or so down hill, it’s not as big of a loss as the phone would be. (The penlight survived. The phone, based on the unhappy noises behind me, did not. Not my phone, not my problem.) As you can see from the photo above, I had both.
So, I highly recommend carrying a small flashlight as part of your travel kit. Get one you can palm, with a narrow beam, and that takes common batteries.