A good underlay insulates against sound, stops rising moisture, and eliminates small irregularities. That is why it’s an essential part of the floor.
Luckily, it’s easy to install as well. All you need is a knife.
How shoud I install it?
Remember that your underlay needs to be as smooth as possible. So, never put two layers on top of each other: this will create unevenness. Immediately secure the first sheets of underlay with a laminate board and work towards the wall.