In Builder Barracks level 11, Hog Gliders are the final and eleventh troop to be obtained; to do so, you must first unlock Builder Hall level 9.
Strategy
Offensive Strategy: The ideal way to use hog gliders is surgically, not in large quantities. The majority of the Stunning Glide stun from the earlier Hog Gliders will be lost if additional Hog Gliders are quickly deployed onto the same defense (as it is overridden by the stun from the last Hog Glider to hit the defense).
Defensive Strategy: Keep your most important fortifications out of the Hog Gliders’ line of sight to avoid stunneling them. Placing relatively little fortifications, such cannons, on the front lines to eliminate gliders or absorb damage and stun can be a smart tactic. But keep in mind that if these defenses are not well-defended, the ensuing Hog Rider may still demolish them, allowing further Hog Gliders to penetrate farther into the fortress.