There's no other item quite as useful when having a barefoot horse than a good hoof boot. There is, however, more to selecting the ideal boot for your horse than you might think. There are a wide variety of brands and types of boot on the market today, and which one you choose should be determined by two important factors: your horse's hoof shape, and your intended activity.
The first factor has to do with the shape of the sole of the boot and it is important because some boots are designed to fit round hooves, while some fit wide hooves best, and others fit petite hooves. To some extent, if you have an 'average' hoof, it will fit reasonably well regardless of the type, but - and this is especially important for those of us with pathological hooves to think about- if the hoof is mis-shapen (by abnormal growth or injury) or in the process of rehabilitation you may have to change boot types a number of times as and when the foot shape changes. For example: If your horse developed severely under-run heels and flared quarters (as this picture demonstrates) then you will need a boot which will accomodate as wide a foot as possible (as well as a pad), but as the foot rehabilitates you will soon find that a more round-shaped boot will do the job nicely.
Perhaps just as vital is what you plan to do with your horse- whether it be endurance rides across rocky ground or carriage driving on asphalt roads, each discipline will suit a particular style of boot. This is where we will consider the types of fastening and upper materials. Included in this consideration is also whether your horse is being booted as part of an ongoing rehab (where, I'm afraid your choice may be limited to the accomodatingly roomy trainer type boots) or if you just need a bit of extra insurance if and when your horse may be a bit tender (in which case there are many sleek and stylish options open to you).
Next up: Part II: Sizing Your Hoof Accurately