Very long but thorough fitting process explained right here!!
I work at Rock/Creek Outfitters in Chattanooga, TN and very knowledgeable about boot fitting. In fact, we get written up if someone comes to try on a boot and we do not fit them using "fit cards"
The first question we ask is what they will be using it for. Light hiking, backpacking, cold weather, etc and the level of their experience. Based on their answer, we then determine if the customer needs a high boot, mid, or low hiking shoe...or trail runner. We then give them a brief explanation on wool socks and give them a pair to try the boots on with. Very important.
Before we put the socks on, we self assess the foot's volume. This is helpful because we know some of the boots have large volume and some have a little less.
The next step is to set the person on our bench and sit across from them on a special stool that has two pins on it to hold the measuring tool. We line the knee up with the shoulder and bend the knee to a 90 degree angle and place the foot in the measuring device, WITH the sock on. This is the unweighted measurement. We size each foot, getting length measurements, heel-ball measurements, and width.
The ball of the foot is measured using the vertical slider on the measuring device. The fitter is supposed to feel for the notch that connects the big toe to the rest of the foot. Sometimes it is hard to find so we instruct them to raise the big toe. Not to be confused with the bone itself, it is actually a ligament we are feeling for.
Then we put two measuring tools together, shoulder width apart, and tell the customer to then stand on both of them. Getting the weighted measurements of length, heel-ball, and width.
The next step is doing math to figure out the difference in each of the numbers. The average person's foot length increases about half a size when they put weight on the foot. Same with heel-ball measurement. If the customer's foot length is a 9 and the heel ball length measures at an 11, this lets us know that they have short toes and might fit best in a 10 or 10.5, because the ball of their foot hits farther up the boot. If you try to fit them in a 9.5, you might find that the ball is hitting an uncomfortable spot on the shoe, which will cause friction and blisters. Another reason for finding the heel-ball measurement is finding how much of an arch they have. A "flat-footed" person's ball measurement is likely to stay the same when weighted. Someone with high arches or a heavy pronator is likely to add .5 to up to 3 sizes when weighted! One of my coworker's has a right ball that extends half a size and a left ball that extends 3 sizes.
This is when we educate the customer about superfeet. We recommend them to everyone because they give support that all hikers need. If you take the inserts out of your boot right now you will see the lousy excuse for an insert that is included. The manufacturers are not concerned with your physiology, just the foot itself, protecting it from the elements. You might consider custom orthotics (superfeet custom) if your arch extends over 1 size. This is a red flag for plantar fascitis.
The size of the boot is determined by the 3 factors measured on the tool. The weighted foot length gives us a starting point. A size 9 usually requires a boot that is at least size 9.5. Then we just go from there, giving our expert opinion on which shoes are suitable for volume and width. We bring out at least 3 different pairs and put superfeet in each pair, then lace the boot up snug and take the customer to the incline board.
The incline board. Ahhh my favorite. So you take a few steps up the board and stand on the hill. Then we squeeze the heel with our palm and make sure it is snug in place. Then we feel the rest of the boot and make sure there is no extra room. If there is, you tighten the laces and go back on the board. Loose boots equal blisters. If the boot is squeezing the foot in an area or extending off the sole, then we try a wider boot. If it is just one spot that has pressure due to a bunion but everything else fits great, we are able to stretch the shoe on that spot upon purchase if it is leather.
Then we instruct the customer to turn around, stomp 3 times and stand downhill at the bottom of the incline board. Then ask the simple question "are your toes touching the end?" If so, we check the lacing again. Then go back on the board. If it still touches, we get a bigger shoe.
The boot fitting process lasts at least 20 minutes and should last longer with the fitter explaining anatomy of the foot, etc. They should be there offering guidance on lacing techniques, volume techniques, benefits and features of each boot. I highly recommend the custom superfeet because they basically cured my plantar fascitis. This also takes 30 minutes. Try on as many boots as possible in your category and find the one that fits you best that you are confident you can put hundreds of miles on if need be. Boots, like a car, are a big investment and your feet can take you places cars can't!
It didn't take me long to learn how to do this and honestly. I've been in the industry less than a year but my level of care for the customers exceeds my leisure time at work. Most places just dont take the time because they are lazy. Insist that they do it right or don't do it at all. Also, I never try to sell anything. If we don't have a boot that will work for someone, I will point them in the direction of a place that does. Often times I recommend Zappos due to their free return policy. They are more than welcome to do the fit test with me after buying a different boot elsewhere.
Common misconceptions about boots are that one brand's sizings are all the same. Not true. Each boot by a manufacturer has a completely different fit.
Common misconceptions about feet are that a flat footed person doesn't have an arch and doesn't need arch support. Not true either. Everyone has an arch and everyone benefits from arch support. It may take getting used to, but having something there regardless of the size of the arch greatly reduces foot fatigue.
Feel free to ask me any questions or come visit me for a fitting