Scent marking is a very normal and common behavior that is not usually an issue when it is done outdoors. Both sexes scent mark, but unneutered males are usually the worst offenders because testosterone stimulates signaling of sexual availability and claiming of territory. Resources such as toys, food bowls, chew treats, bones, and beds are the most likely objects to be marked, and in some cases, a dog will actually mark a person or something that smells heavily of that person, such as a sofa or bed. Scent marking is also more common in multi-dog households where dogs compete for space, resources, and human attention.
In many cases, neutering can significantly reduce the desire to scent mark, but if a dog is a serial scent marker before neutering then surgery might not reduce the behavior completely. Boredom and lack of mental stimulation and physical exercise can exacerbate marking behavior, so be sure your dog gets the appropriate amount of exercise and mental stimulation.