After rescuing Leia from the Empire, Luke and Han Solo are trapped in a garbage compactor. Han tries to blast the door but his blaster shot bounces off many times:
Why did Han Solo's blaster shot bounce so many times in this scene?
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As Luke said to Han, it's the magnetic seal also called a vacuum seal. It is a technology that used electromagnetic fields to lock metal parts together. Although not quite explained in the movie it implies that Luke, Leia and Chewie have already gone through that near-death experience, Han subjected them to it all over again. That wasn't shown in the movie to keep the narrative and to emphasize on Han being a hot-head who doesn't answer to anyone.
That technology appeared in many Star Wars games like Star Wars: Edge of the Empire and many other RPG games.
The script indicates that the doors and wall are metal This is, apparently, something that will reflect a blaster bolt at a short distance.
Han draws his laser pistol and fires at the hatch. The laserbolt ricochets wildly around the small metal room.
Everyone dives for cover in the garbage as the bolt explodes almost on top of them. Leia climbs out of the garbage with a rather grim look on her face.
The junior novelisation, on the other hand, notes that the door and wall are magnetically sealed, and thus blaster-reflective. Quite how one magnetically seals a wall isn't described in any detail (and frankly seem to be a typo/misunderstanding on the part of the novelisation author) but there you go.
Too late. Han fired at the hatch, and the laserbolt ricocheted wildly around the metal-walled chamber. Everyone dived for cover until the fired bolt’s charge ended in a small explosion that didn’t even dent the metal wall.
Chewbacca turned to a wall and cowered. Despite the hazard posed by the magnetically sealed walls, Luke and Han held their blasters out, ready to fire. Han said, “It’s worse.”