In message .com,
Stephen writes

What do you mean by "heel"? I know you're definitely not referring to
your own feet!

A heel cutting consists of a (short) side-shoot together with a small
piece of the adjoining side of the parent shoot. There's plenty of stuff
on heel cuttings on the web, if you wish more detail.

A heel cutting is often what you get if you try to break off a
side-shoot manually, rather than using secaturs or a knife.
--
Stewart Robert Hinsley