One nail at each end cap of the awning. There was one hole straight through the shaft. Then two slots in the small (about 1" diameter) end of the cap. Slots were at 90*. Small nail, 6d maybe 8d, might have used drywall nails, through slot and hole, one at each end. Because the slots are at 90*, you only have to turn the thing a little ways to catch alignment of the hole with one of the slots. Then you can put the nail, cotter pin, etc. through from either end. I went out and looked at a box of 4d "box nails" and they didn't look as big as what I remember using, but I think they would have worked.
EDIT: You're taking me back a long time, but as I recall the shaft is only about 3/8", making the hole through the shaft less than 1/8". So the pin can't be near 16d.