Holdable objects are those that the player holds and walks around with. You can hold them by dragging them like a Body object or by hitting the Spacebar key in front of it when placed down (you can throw a Holdable away with the same key). The direction of which they're thrown will depend on the direction you are moving when throwing it.
They will fall and disappear after being thrown. If they collide with a Liquid object or a Harmful/Deadly object, they disappear immediately. If they collide with a Crumbling object, the crumbling disentigrates.