a.k.a. F Puzzle
Old design, 3D print files made by Fernando Jerez, 2016.
(Printed on a Monoprice Mini V1 3D printer at scale 160%,
from Thingiverse thing 2975065, 2019,
PLA plastic, 4 pieces and tray 2+1/4" x 3+3/4" x 3/16" inches)

An easy puzzle to pack the four F's into the tray:



Further Reading
Four F's Puzzle Thingiverse Page, from: http://www.thingiverse.com/thing:1666559