In technical terms, the memory stick is a product that is
assigned a new meaning and is thus referred to as the target of
the metaphor, while the padlock is called the source, the entity
that modifies the target in order to convey that particular meaning.
The meaning in question is the “data security” provided by this
particular USB, which the designer has emphasized by fashioning
the product into a padlock (see Figure 2). This fashioning process,
called mapping, physically builds metaphorical links between
target and source by projecting properties of the source onto
compatible properties of the target. In our example, the mapping
process involves an explicit projection of a padlock’s form and
usage onto the form and usage of a memory stick.