As you explore the planet Atropos in Returnal, you will find many treasure chests out in the open on ledges or in hidden alcoves. Most of them provide no more resistance than a possible cloud of malignant vapors, or a lock you must open with a key. Some of them, however, are locked away by the environment itself.
If you come across such a chest in the first biome, you will find a series of vertical columns, like prison cell bars. Neither your sword nor your guns can eliminate them directly, so you must look for an alternate method.
The trick is to find a switch panel on a nearby wall. It is orange, with a circular patch of light glowing at its center, and it can be easy to miss if you’re not looking for it. Sometimes, the panel is directly overhead, or on a wall to the side. Other times, you may have to circle around the area slightly.
Wait until you have eliminated any nearby enemies that might serve as a distraction, then start your hunt for the switch. A single shot from your gun will trigger the switch and eliminate the irksome bars so you can approach the chest without further resistance. You’ll never have to look far to find the switch, but sometimes it is hidden behind a destructible stone statue or similar obstruction.
Since the items in those chests tend to be better than usual, it’s worth spending a little time hunting for the switches that let you reach them.