Designers generate metaphors by tak

Designers generate metaphors by taking an attribute(s)
from one entity and transferring it to a product they are designing.
For instance, in the product metaphor seen in Figure 1, the
designer implies an association between a memory stick and a
padlock. Rather than building a piece of software into which users
type their passwords, the designer forces users to use a real key
to release the shackle and access the data. A padlock is an object
representing “security.” An explicit reference to this object helps
users to see the expressive intention of the designer: Unauthorized
people do not have access. For this reason, the padlock metaphor
provides the users with a novel, yet straightforward interaction
with the product.