Railroad spikes are often used for protection of property and self. They can be nailed down in the corners of your property to protect your home. They can also be placed in your vehicle to protect from accidents and theft. 
In addiction, they are great for grounding and banishing work, as well as prosperity rituals. 
They have many magical benefits and hold a very powerful energy. 
Often they are used in hoodoo, but are not exclusive to that closed practice.
Side note: for obvious reasons it is illegal to collect railroad spikes from tracks. These were responsibly and legally sourced.
1 spike for $5.55