The empty broken cannon stand is used when repairing dwarf multicannons within the Artisans' Workshop. The filled version can be picked up from the cannon stand desk in the repair workshop after the cannon base has been repaired, and then it can be dismantled to remove 3 broken pipes from the stand, leaving the empty broken cannon stand. The pipes should then be fixed and reattached to the empty stand to make a fixed cannon stand.
This item cannot be taken outside of the repair area. It can be re-obtained from Aksel if you have left the area after obtaining it.