How to Make an Item Frame Invisible in Round's Invisible Frames Mod
Toggling a Single Frame
Making one item frame invisible is the core action of this mod. Walk up to the item frame you want to hide and make sure you are close enough that the game highlights it as your target. Hold your sneak key (default is Shift) and, while still sneaking, right-click the frame. The frame itself should disappear, but any item you placed inside it stays visible and floating in place.
If nothing happens, check three things: you are actually sneaking (not just crouched in a menu), you are aiming at the frame and not the block behind it, and you are not holding a tool that overrides right-click on frames. Empty your main hand if you are unsure.
Making It Visible Again
The toggle works both ways. Sneak and right-click the invisible frame again to bring the frame border back. Because the frame is invisible, you may need to aim carefully at where the frame used to be — the item inside is usually the easiest thing to target. If you removed the item first, hover over the empty space where the frame sits and sneak-right-click there.
This is useful when you want to swap an item out, since you can briefly reveal the frame, change the contents, then hide it again.