The metal tips were fitted hot and glued with Suberin. For the Surberin glue, I collected birch bark for hours in a wetland. The distillate becomes mixed with charcoal.
This composite adhesive early humans does not lose its adhesive power or elasticity. Our ancestors used this nature glue to attach their arrowheads.
I suppose birch bark glue was an intercontinental bestseller. Even the Egyptian chariots were sometimes glued make some with Suberin. Not a few components of this high end warrior chariots consist made of European wood.