PRODUCT FAMILY
Fastener and fixings products have over time developed product families.
A good idea for a head or drive type can extend over a considerable product range as the method of production is developed and proves to be advantageous. Some of these families have developed over centuries but most within the last 100 years.
Links:
BOLT MACHINE SCREWS
SCREW PARALLEL THREADS SCREW TAPERED THREADS
NUTS WASHER
SOCKET SCREWS STUDDING & STUDS
SHEET METAL
PINS
CIRCLIPS
PLUGS
FIXINGS
Looking at the linked pages above will give you an insight into how the product families have developed and the possibilities for future change.