I am not certain what this was used for.....It is a metal opening/closing ?hook with a chain on the top - ?hay or ice hook?  It is completely rusted.  With the lower hooks together and the chain extended upward in the center it measures about 16 1/2" in H x about 4 3/4" across the overlapped hooks on the bottom.  The upper chain links measure about 1 1/2" x 1" x just over 1/4" on each link, there are 14 links.

Metal tool with Chain top