U mnie w słowniku flek to - heel tip
zdarte fleki - worn-out heel tips; wymienić fleki w butach - to have the heel tips replaced in one's shoes
a w Sieci znalzałem takie definicje:
Heel Tip
A metal heel plate [OED 2d Ed.]
http://www.personal.utulsa.edu/~marc-carlson/shoe/RESEARCH/GLOSSARY/bdefh.htm
heeltap
1. A layer of leather or wood added to raise the heel of a shoe; a lift.
2. A small amount of liquor remaining in a container or drinking vessel.