Mitre joint in oak
A mitre joint in oak joins two pieces with matching angled cuts so their meeting faces form a corner. Oak is the timber used for the pieces.
The mitre
The ends are cut at matching angles and brought together at the corner. This makes the joint line run diagonally across the ends rather than square across them.
Oak in mitre work
Audels (1923) names white pine or oak as preferable woods for mitre work. The same passage warns that other woods may warp or split with climatic changes and steam heat, causing the cuts to vary and go out of true.