noun
hex key; Allen key; Allen wrench
A tool used to drive bolts and screws with a hexagonal socket. 六角棒スパナ is the common Japanese term; 'Allen key' is a trademarked name often used generically.
この家具を組み立てるには六角棒スパナが必要です。
You need a hex key to assemble this furniture.
Compound of 六角 (hexagonal) + 棒 (bar) + スパナ (wrench, from English 'spanner').