The Trophy Mount is a furniture you can build (the Indoors page).
In-game description
A walnut board with a brass nameplate. E it to hang any legendary fish you have ever caught, at full size for all to see; E again for the next. The fish stays yours.SHOWN IN THE BUILD RING
Building it
It costs 6 
Wood, 2 
Iron Ingot, 1 
Pearl. Take it down with DISMANTLE to get its cost back (see Building).
