No Stupid Questions

I always wondered about the approach I’ve seen in a couple movies …. Could you save yourself by tackling the bad guy onto the grenade and being on top of him. Aside from the impossibility of being in a situation where that makes sense, and reacting quickly enough, would the bad guy contain both the shards and the pressure enough to save everyone else?

Toss it in a water bucket buried at least 4 ft below ground. My guess is that would actually work pretty well.

Not a direct answer to the question, but relevant; they make a film you can put on your windows that holds them together when shattered. This could theoretically cause a grenade to bounce instead of penetrating. Not an expert, do your research before assuming it will work.

first, don't be there, then don't be detected, then don't be hit

wall (brick or concrete, not cardboard) between you and grenade should stop fragments, anything less is heavily dependent on what kind of the thing it is and how lucky you are. ikea chair won't save you, anything solid enough to be worth it would be so heavy that time spent moving it is just better spent moving away. if you live above ground floor, like on third floor or above, it's likely that you'll be fine because throwing grenades up is a really bad idea. grenades are round and roughly as heavy as rocks of similar size, perhaps you can get laminated glass windows that should crack but not let grenade through on impact

You will know for sure that a hand grenade is going to explode right in the next moment when it becomes slightly bigger and you see a few cracks on the outside.

1. easily will break glass, they’re heavy, dense, and hard

2. hit the deck, the explosion will be up and out

3. shrapnel is how fragmentation grenades kill, not the overpressure wave

1. Should be as easy as throwing a rock.

2&3. Both pressure and shrapnel are deadly. For pressure, imagine a bubble machine blowing bubbles. You could poke them and they pop. A slight breeze could pop them. This is due to a pressure difference. When an explosive creates a pressure difference, the cells of your body are like the bubbles. They pop. Pressure will have a hard time getting around solid objects. A wall or a chair might be sufficient. Shrapnel will be more difficult. If this is truly a concern, I'd suggest having a "decorative" metal pot. If you could cover the grenade with it, that could potentially nullify its effect. Put as much matter and mass between you and the explosive as possible. If you have nothing available, lay on the ground with your head furthest from the grenade and your feet pointing towards it. Basically you would want to be able to draw a straight line from the grenade through your feet and out your head. Because that's the direction the shrapnel will take.

Edit: some people in the comments with a fundamental misunderstanding of how weapons work. A grenade is a purpose built weapon that was designed. If you took the explosive out of a grenade, put it in a metal pot with the lid welded on, and detonated, you'd just have a mangled pot. Pots won't break up into shrapnel it's gonna look like the T1000 after getting shot with the grenade launcher. And any shrapnel that makes it through, will have its kinetic energy severely reduced.