In Kingsman: The Golden Circle, In the scene where Merlin briefly freezes the landmine trigger, pushes Eggsy off, and holds down the trigger with his own foot instead, why didn't he just use a rock or something instead?
There is a certain amount of poetic license used in this scene.
Although it could be argued that the rock could have unexpectedly rolled off and killed them all. And perhaps there wasn't enough time to place a rock after Eggsy got off.
If you want to dissect landmine plotholes, many argue that landmines would simply go off as soon as pressure was applied to them, for effectiveness, as discussed on this TV Tropes article.