You
may wonder what a ‘reservoir’ is, well it basically stores a supply of
ink for your nib, therefore allowing you to write or draw more before
the need to re-dip the nib. The reservoirs are usually brass coloured,
have a slight bend to them and have two small ‘lugs’ that allow the
reservoir to be fitted to the nib. So - once you have your nib fitted in the holder and it is a suitable size to take a reservoir, then it’s time to fit one to the nib.

When fitting the reservoir, hold the reservoir in your left hand,
in-between your index finger and thumb with the lugs pointing upwards
and the pointed end of the reservoir pointing to your left. Take your nib in it’s holder in your right hand and gentle slide the nib between the lugs until the shoulders of the nib are between the two lugs.
It may seem tight or loose but that can easily be remedied. So now you have the reservoir attached to the nib but you need to adjust it for it to work correctly.
Turn the nib over and have a look at the under side.
The point of the reservoir needs to be about 1/8th of an inch (0.3 Cm) from the tip of the nib tines. Slide the reservoir until it is in this position.
If the reservoir was tight when you fitted it you will need to check that it is not causing the tines of the nib to be forced apart by pressing up against them. If this is the case try easing the reservoir back slightly or gently easy the lugs away from the shoulders of the nib. They are easy to bend so not masses of pressure. Repeat until the reservoir fits snugly to the nib without wobbling and the pointed end just touches the tines.
The reservoirs can be fitted to the likes of Round Hand nibs, square cut nibs and italic nibs.
