Iron Nails are used in work to nail something down, to “hammer something in” or to cause suffering or pain. 
For example, one might take iron nails and wrap an enemy's hair around them. This might get nailed to an accursed tree such as blackthorn, yew, or cypress. Nine nails can also be placed in a jar with nine needles, nine pins, sulpher, dirt from the cemetery cross, the dirt off seven graves, urine, plants of malice, such as locust or blackthorn thorns, crown of thorns, cemetery spruge, bull nettle, etc. as well as black pepper, and chili pepper. Combine with a photo of the person, as well as goofer dust or crossing powder, and bury somewhere close to them, preferably on their property.
To dominate the thoughts of someone, take seven iron nails and a skull candle, anoint them in domination oil, and urine and hammer them into the skull, each time receding your wishes.
Each purchase will come with 3 iron nails, about 1" long.