Fastener having recessed, non-circular head, and fastener-driving tool

A fastener, comprising:

• a head;
• and
• a shank having a threaded portion;
• said head and said shank defining a longitudinal axis through said fastener;
• said head having an external portion which has a configuration which is non-circular when viewed axially so as to adapt said head for driving coaction with a driving member having a socket shaped similarly to said external portion of said head so that said socket can be axially fitted over and about said external portion of said head so as to define a driving relationship therewith;
• and
• said head has a recess extending axially into said head, and a continuous, upper edge portion having a configuration which comprises a regular polygon and which separates said external portion of said head from said axially extending recess of said head, said axially extending recess having a polygonal configuration for cooperating with a similarly configured centering pin fixedly associated with said socket of said driving member so as to guide said centering pin of said driving member from a radially offset position with respect to said longitudinal axis of said fastener toward said longitudinal axis of said fastener and thereby center said socket and said head relative to each other, and for defining an additional driving coaction with said centering pin of said driving member in addition to, and in conjunction with, said driving coaction defined between said socket and said external portion of said head of said fastener.