Intermediate Sliders;

Intermediate sliders are what attaches the sail to mast Between the full batten holders. Some sails have 1 intermediate between the head and top batten, one between each full batten and then one between the the bottom batten and the tack.

Other sails might have none at all, others maybe 2 between each batten.

Keep in mind the more sliders you have the higher the sail will stack above the boom.

There is no specific rule this, it is sailor option.