I sometimes used a clover leaf cutout on frames I built in England during the 1970s as did many other framebuilders of that era. It was simple; just drill 3 holes, and the triangular shape lent itself to the shape of the lug. (See below)



Also some Prugnat lugs (Made in France.) came with the arrow head cutouts already in them as seen on this Paris Sport frame I built in 1979.
http://photos1.blogger.com/blogger/2...eadtubeCrp.jpg