Zills ("sagât" in Arabic) are small metal cymbals held in the palm of one’s hand. They are percussion instruments used in traditional music-making and they give a typically Eastern flavour when played. Gypsy dancers (ghawazees) and Eastern dancers use them too with more basic rhythms to accompany their movements.
It is probable that they have ancient origins and are similar to the family of the sistrum, crotalum, castanets and other small hand-held instruments used in ancient cults and festivals, especially those in praise of the goddess Cybele.
There are various examples seen in Golden Age films in Egypt (especially the famous dance of Naima Akef in "Tamerhenna"), but dancers tend to use them less nowadays. They are still widely used in Turkey.
The video seen below is another famous scene from the Lebanese film "Safar Barlik", with music from the Rahbani brothers.
Zills can be used to make various rhythm combinations with, to a certain extent, changes in tone. Here are some examples of zill rhythms which can be played to accompany dance.