«Missing Middle» was coined by Daniel Parolek of Opticos Design, Inc. in 2010 to define a range of multi-unit or clustered
housing types compatible in scale with single - family homes that help meet the growing demand for walkable urban living.
It's worth noting that Schlage and Kwikset keyways (and thus keys) are not
compatible with each other so if the rest of the
house is keyed with one
type, replacing a lock with a different
type can be an expensive or annoying mistake (having to replace all your other locks or carrying around two
types of keys).