Put it in your house.  The weight your house currently contains will go down by 1kg, giving you an extra 1kg of new space to use.

Sandy

Extra Houspart => Placing this item inside your home will increase its capacity by 1kg. 

It

 cannot be robbed once inside your home.  
The "it" on the second sentence refer to what? Is it the house or the extra houspart?
Please reply. 
Thank.

The Extra Housepart cannot be robbed.  Nothing can entirely stop you from being robbed except maybe good traps.  As even the highest lvl chars in larki cannot even keep out the highest lvl robbers all the time, its hard to not be robbed once and a while.

Pyratic