Caponier

[2] In some types of bastioned fortifications, the caponier served as a means of access to the outworks, protecting troops from direct fire; they were often roofless.

In later polygonal forts, caponiers were often roofed and were not intended as a type of covered way, but as the main way of keeping the ditch clear of a besieger.

As polygonal fortresses evolved, caponiers became more substantial, higher and protected above from plunging fire with masonry and earth cover.

In late 19th century, works which were largely underground, caponiers were reached via a tunnel from within the fort.

An alternative to the caponier is a counterscarp battery, dug into the outer face of the corner of the ditch, giving a similar field of fire.