"Horizontal slats" refers to thin, long strips or bars that are arranged horizontally (parallel to the ground) either vertically or in a specific pattern. Full definition
The updates on the 2015 Holden Cruze include a reworked front grille with horizontal slats instead of honey comb detailing. (motorbeam.com)
The robust, horizontal slats of the air intakes provide a solid counterpoint to the dynamic design of the front apron and add further detailed emphasis of the front - end's traditional X-model character. (motorshowblog.com)
Other changes include the addition of thin black horizontal slats in the upper grille, which now connects with the headlamps. (drivemag.com)