Shoes: The popular custom of tying an old shoe to the back of the car in which a bride and groom are setting off for their honeymoon is a specialized form of what was once a widespread practice, that of throwing an old shoe at or after someone to wish them luck, especially on a journey.
Another practice, generally interpreted as defensive magic, was more secretive. As Ralph Merrifield writes:
There are few local museums in southern England that do not possess a few shoes, mostly dating from the 17th to the 19th century, that were found hidden in old houses, usually in a wall, roof, or chimney breast, or under a floor...deposited in places that are normally accessible only at the time of building or structural alteration, or by taking considerable trouble at other times, for example by raising a floorboard.
The only first-hand explanation recorded is this comment from Lincolnshire: "In the old days, a lot of kids died young, so to keep part of the kid with them, or the spirit of the kid if you like, a shoe was buried in the wall of the house so the kid was still with them." ... Explanations as to why shoes should be considered protective can only be conjectural; the two main ones are that they are dirty, especially when they are old...and that they symbolize the female sexual organ. Small model boots or shoes in various materials were used as mantlepiece ornaments "for luck", or as "lucky charms" in jewelry. (Oxford Dictionary of English Folklore)