The Hotchkiss H 39 is a small tank at 4.22 metres long, 1.95 metres wide and 2.15 metres high.

The bodywork is made up of six cast steel sections bolted together. There is the engine floor and that of the cabin which together make up the base of the vehicle, and four sections forming the upper bodywork: one to the front, one to the rear and two sides.

The use of cast steel allowed the armour to slope slightly and thereby avoid becoming a trap for shells and it also maximised the chances of deflecting a projectile.

Although good for the time, the armour did not satisfy those in charge of the Infantry, having a maximum thickness of only 34mm against the 40mm asked for. Additionally, there were many problems relating to the quality of the armour including, for example, the fact that a large amount of it was sub-contracted.

Too soft at first, the steel was subsequently hardened but then became brittle and full of bubbles and the bubbles were just so many weak points.