The Ceiling Cap
You use a ceiling cap to hang a hanging lamp neatly and in the ceiling cap the hanging hook, the lamp cord and the terminal block "disappear". Then it looks tight again.
Ceiling Cap directly On Cord
In this case, place a strain relief under the ceiling cap to get it neat and tight against the ceiling.
So you are not working with a slip ring now. These have a metal screw and you do not want to screw it directly onto / in your cord; then you can get a short circuit.
Ceiling Cap and Pendant (Hanging) Lamp on a Pipe / Pendel
In this case, place a slip ring under the ceiling cap. Some ceiling caps already have this attached as standard. Some caps do not have this and then you have to buy the slip ring separately.
Measure the outer diameter of the rod of your pendant lamp with a caliper.
Common sizes are 1.0 cm / 0.39 inch (M10) and 1.3 cm / 0.51 inch (M13). But other diameters also exist.
Cap and Pendant (Hanging) Lamp on a Chain
See explanation above, with hanging lamp on pipe / pendant. Same story. The pipe in this case is a short piece of tube with an eye to which the chain is attached. This short pipe is also called an adjustment pipe. In this case you also work with an slip ring.
Hang up a very Heavy Lamp
We have a separate page for this with information: hanging heavy lamp