first edit your clientside , look foritemslotcounttable.txt and open it and then ,add the item number of your item
for example Lord Kaho horn
5013#1# <------------------- 1 = the number of slot
and then save it
make a patch!
Second , go to your item_db
edit 0,0xFFFFFFFF <------------ the first 0 = the number of slot.
and then save .
type @reloaditemdb or restart your server.