To get the bosal to fit a horse’s face, when it is newly made, you shape it.
There are good photos of wood bosal shapers. Kip Fladland makes one, it is the most recommended one I have found from the sources I trust.
These sources also tell me a large can (soup, pumpkin, salsa…) works just as well.
I took a few photos:
Bosal on can, top view:
http://s262.photobucket.com/user/Buxombeefcowdairy/media/Buck%20clinic/PIC_0005.jpg.html?sort=3&o=2
You can see from the photo, that not only have the shanks been ‘expanded’ at the bottom in order to not pinch/scrape the jaw, but also that the nose has been pulled in.
After the bosal is shaped, it will keep this form:
http://s262.photobucket.com/user/Buxombeefcowdairy/media/Buck%20clinic/PIC_0007.jpg.html?sort=3&o=0
I ‘store’ my bosals on their pumpkin can…except sometimes for a few days around Thanksgiving!
AFTER you get the bosal in a good shape, the best thing to do with it is ride in it. I have heard that the more they are used, the better they get.
A word of warning, though:
The bosal will ‘tell’ you what holes you have, what you don’t do very well, in the snaffle. There is no problem using the bosal some, especially to find the things you and your horse aren’t really doing well, yet.
If you go to a Buck clinic, and you are not in Buck’s opinion ready to be using a bosal…
…and you are lucky, Buck will tell you that, reasonably privately/one-on-one, during maybe the second or third day. That you need to (say, have your horse carrying a soft feel through the haunches in, or that your horse should be doing simple lead changes, carrying a soft feel, or maybe more generically that you need to get some things working in the snaffle) before you go to the bosal and possibly ruin or backtrack significantly your progress toward making a bridle horse.
…and if you are not lucky, Buck might tell you (on the last day of the clinic) VERY loudly over the loudspeaker that "SALLY, YOU HAVE NO BUSINESS IN THE BOSAL. Your horse is doing x, y, z and etc and you need to go back and get these VERY BASIC things going…
I’ve heard both.
My goal, which I am hoping will happen this summer, but due to some health issues might happen in another year, is to go to my Buck clinic and have him tell me it’s time (or close to time) to hang a bridle bit on my horse.