On Thursday, September 19, 2019 at 10:47:57 AM UTC-7, dpb wrote:
Have new hardwood floor going in...access to crawl space in closet is
thru a opening in the floor...

Easiest hardware-wise is to frame in an aperture, and simply drop a
flooring panel into it. Hinges for such a 'door' are unlikely to
work well (flush hinges? geting dirt dropped onto 'em?).
A minor discontinuity at a floor-panel edge is not likely
to trip anyone, because it's in a closet.

You'd want to panelize subflooring and frame, the 'door' has to be
as sturdy as the rest of a floor.

Recessed handle, or even just an oval aperture (manhole-cover style, for
a lifting tool) will suffice for opening. If the panel could be rested in
an upright position, with a latch or drop-into-slot feature to keep it
from flopping closed, that'd be a bonus.

Real hardware doors can also be store-bought, like
http://www.cellaraccess.co.uk/Fire%20Door.html
and all it takes is... money.