In general a Hymenochaete fruit body is just a flat sheet on the woody substrate. The fruit bodies are mostly found on the underside of fallen, dead wood. If a fruit body forms on say the sloping side of a fallen trunk, then it may become what is termed effused-reflexed. The lower (effused) part is a flat sheet on the wood but in the upper (reflexed) part the sheet bends out from the wood to create a short shelf-like outgrowth.
Most species are some shade of brown and often the marginal area is brighter than the rest of the fruit body. A few species are a purplish red. In effused-reflexed species, the upper surface of the reflexed part usually has short hairs.
In an effused-reflexed fruit body the fertile area (with the spore-bearing basidia) consists of the effused part and the underside of the reflexed part. Naturally, where the fruit body is totally flat on the underside of dead wood, the whole of that surface is the fertile area.
If you look at the fertile area with a 10 times hand lens, you won't see basidia, but you may see numerous, dark brown bristles (or setae). This is a feature of Hymenochaete and helps you make an educated guess of this genus in the field. Setae vary in length and are easier to see in some species than in others. When I'm collecting specimens I may need to hold a specimen up at varying angles to my eye, in order to get the light just right to make it possible to detect the setae.
The genus is found on many types of wood in a wide variety of habitats.