The bounce before the wall
Your opponents' ball has to bounce on your floor before it touches any of your walls. After that bounce, the glass and the mesh are part of the game and you play the ball as it comes off them.
The one rule that matters
When the other pair hit the ball, it must cross the net and bounce on the floor of your half before it touches your glass, your mesh or anything else on your side. If it hits one of your walls first, the shot was out and the point is yours.
After the bounce, anything goes
Once the ball has bounced on your floor it can hit the back glass, the side glass, the mesh or several of them, and it is still in play. You can hit it at any moment before it bounces on the floor a second time, including after it comes back off the glass. Two bounces on the floor lose the point, whatever it touched in between.
Using your own walls
You may hit the ball into your own glass so it rebounds over the net. That is legal as long as it then crosses the net and lands on their floor before touching their walls. It is a last resort, usually when the ball has got past you, and it has a name: the contrapared.
The mesh and the frames
In a rally the metal mesh and the frames that hold the glass count as part of the wall: after the bounce they are fine, before the bounce they are out. They do not return the ball like glass does. Mesh kills the pace and frames send it anywhere, so give yourself more room near them.
Your shot into their court
The same rule works the other way. Your shot has to land on their floor before it touches any of their walls. A ball that bounces in their court and then hits the back glass is a perfectly good shot. A ball that goes straight into their glass is out, and so is one that hits your own mesh or your own floor on the way.
Spørsmål
Can the ball hit the glass in padel?
Yes, after it has bounced on the floor of your half. If it hits your glass before bouncing, the shot was out.
Can you hit the ball into your own wall?
Yes. You can play it off your own glass as long as it then crosses the net and bounces in the other court.
Is the mesh in or out in padel?
In a rally the mesh counts as wall: fine after the bounce, out before it. On the serve, a ball that touches the side mesh after the bounce is a fault.