 The trials with the Chesma greatly affected the armour protection design of the Borodino @-@ class ships . The Krupp cemented @-@ armour plates were sized to match the frames to provide support for their joints , and they were locked together with mortise @-@ and @-@ tenon joints to better distribute the shock of a shell 's impact . The 237 @.@ 5 millimetres ( 9 @.@ 35 in ) waterline belt covered the middle 151 @.@ 2 metres ( 496 ft 1 in ) of the ship . It had a total height of 5 @.@ 015 metres ( 16 ft 5 @.@ 4 in ) , 3 @.@ 375 metres ( 11 ft 0 @.@ 9 in ) of which was above the design waterline and 1 @.@ 64 metres ( 5 ft 5 in ) below . It was backed by 75 millimeters of wood to make a better fit between the hull and the armour . The remaining portion of the waterline was protected by 125 @-@ millimetre ( 4 @.@ 9 in ) plates backed by 50 millimetres ( 2 @.@ 0 in ) of wood . The upper belt was 100 millimetres ( 3 @.@ 9 in ) thick and had a height of 2 @.@ 89 metres ( 9 ft 6 in ) . It thinned to 75 mm forward of the casemates all the way to the bow . The rear portion of the forecastle deck was protected by an upward extension of the upper belt in the area of the forward barbettes and the upper casemates . The upper casemates themselves were protected from axial fire by 100 mm transverse bulkheads . Behind the side armour was an inboard longitudinal splinter bulkhead that was 50 millimetres ( 2 @.@ 0 in ) thick between the middle and lower decks . This decreased to 25 millimetres ( 0 @.@ 98 in ) between the middle and upper decks . The bulkhead sloped away from the edge of the lower deck to the lower edge of the armour belt with a total thickness of 75 mm . The slope was one 50 mm plate of Krupp non @-@ cemented armour ( KNC ) on a 25 mm nickel @-@ steel plate . The forward end of the armoured citadel was protected separately and the transverse bulkhead was therefore only 75 mm thick . The rear bulkhead had no other protection and was 300 millimetres ( 11 @.@ 8 in ) thick between the middle and lower decks , decreasing to 75 mm at the level of the armour belt . 
