Light (small) fortifications
There were two main types of small fortifications built. Their designation reflect first year of their construction, so they are usually described as pillboxes type 36 and type 37. For each of them there exist more variants described by small character added to the type number (so you can find pillboxes of type 36a, 37a, 37b etc.). 99% of them were armed with machineguns only and all of them were manned by regular infantry units.
Pillboxes type 36 can be found usually near to the borders and they brought their guns to bear on the front targets, often located in enemy area. They were equipped from one to three light or heavy machineguns with no use of gun carriages. Walls were quite thin and were safe rather from infantry guns. Because they usually didn't use flanking fires and were not much safe, army withdrew them from use no later than in 1937.
Pillboxes type 37 firstly appeared in 1937. They were usually constructed for flanking fires only and were built in continuous lines. Main armament consisted again of machineguns, but in this case using gun carriages. Pillboxes were also equipped with simple periskopes and handy fans.