hexagon socket head; Allen socket head
Technical term for a screw or bolt head with a hexagonal recess, driven by a hex key (Allen wrench).
This bolt has a hexagon socket head, so you need a hex wrench.
Tighten the hex socket head bolt.
六角レンチ is the tool (hex wrench), while 六角穴付き describes the fastener head type.
hex socket head cap bolt
Standard full form for 'hexagon socket head'.
Abbreviated form, common in technical contexts.
Compound of 六角 (hexagon) + 穴 (hole) + 付き (attached, with). Describes a fastener head with a hexagonal recess.