How do you open the hatch?

[nofsky]

Have you ever tried to open a door, in real life, by pushing it on the side close to the hinges? It's much heavier than if you push on the side of the handle. The same principle applies in Penumbra. It's easiest to open a hatch by pulling close to the edge opposite of the hinges. Similarly, when you open a valve it's much easier to grab it on the edge instead of in the middle.

If you need to move something heavy it can help to grab it and then move yourself with WASD instead of moving the mouse. Also keep in mind that you are also an object in the game so you can't open a hatch if you're partially standing on it (of course, there is no player character model so you can't actually see if you're standing on it).