We may receive a commission on purchases made from links. Having a place to hide spare keys is important for many people.

Brunnian links are a type of nontrivial link – or knot – where multiple linked loops become unlinked if a single loop is cut or removed. Beyond ‘fun’ disentanglement toys and a tantalizing subject of ...

Allowing people into your home or property when you’re not there used to be either leaving a key under a doormat, or a complicated business of sending a set of keys by courier or asking a neighbour to ...