You could call the V shape in a letter M the "vertex".
On Identifont they use this terminology, and call the V shape in the M a "centre vertex".
They describe it like this
The upward pointing corners of the M are sometimes called an "apex", so technically, the M only has one vertex, so there's no need to call it a "centre ...
Flush left, for most English language typesetting, means to align text on the left side without indents or any odd alignment. Indents, or specific variations beyond the flush left, would be specified in addition to specifying the flush left.
In typesetting and editing, flush left is indicated by an open left bracket ... [ See image below.
[ image ...