Originally developed by military forces, ranger pace-counting beads are a great way to measure distances travelled by foot. A set of ranger beads is merely a lanyard with two sets of beads; the bottom section has nine and the top section has four. The beads are moved at various distances to count your total distance walked.
Measure how many steps it takes for you to walk 100m. Now when you walk, for every 100m move one of the nine lower beads up. On the tenth time instead move one of the four upper beads up and pull all nine of the lower beads back down to reset; this indicates that you have walked 1km. You can measure up to 5km with this configuration of beads. Brian's Backpacking Blog has multiple methods of measuring strides and also gives alternative uses for using ranger beads in daily life, such as counting the number of glasses of water you drink each day.
Making a ranger band is dead simple. Just take a little paracord or other cordage and small beads you can find in any craft store or online, and tie it as per the photo above. If you need detailed instructions, you can find them at Instructables.
Of course, many people would prefer to use a pedometer and not have to count their paces, but ranger beads are cheaper, easy to make and don't need batteries. Just because we usually use a GPS to find our way does not mean we should not know how to use a map and compass. If you're a frequent hiker it's worth taking the time to make and use ranger beads once so you'll have the skill if you ever need it.
Measuring Your Distance Using Strides [Brian's Backpacking Blog]