with a conker shell tool
yes its the nut of a horse chestnut tree.
It is the horse chestnut that produces conkers.
Nut.
The cashew nut
Walnut is an edible nut with a smooth thin shell.
The nut with the hardest shell is the macadamia nut. It is difficult to crack because the edible part is stuck to the inside of the shell.
Shell.
Chestnut or as we always called them as children 'conkers' xx
A coconut.
nut
testicle