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According to Classroom.com, boots aren't on fence posts as decorations, rather they were placed there to pay respect. Sometimes a rancher will put a boot on a post or hang a pair of boots on a fence to honor a favorite horse.

Stemming from the old adage “a pair of boots for every hand,” those who work on a ranch can become part of the family since many live and eat on the property. If a favorite helper passes away or moves on, boots may be placed on the fence in their memory.

It's a proven fact that cowboys have a long reputation for getting attached to their boots. Once they begin to wear out, it's not uncommon for a farmer or rancher to hang them on a fence to represent all the hard work the boots made possible.