Explain me why i can place a lantern on my handrail?

here : i select the item for inventory and try to set it.
–> i can the shadow see it is ok but finaly not working

but if i select item already placed and move it on my handrail it is work !

here the result :

so why ?

Unfortunately it is a known behaviour. It is not limited to lanterns. There’s nothing wrong with your handrail. The thing is, Stonehearth currently has problems placing ANY object on top of ANY other object. Crates can’t be stacked “as is” but can be stacked by “move” command. The same with two-level beds etc