XHT Test Tile will be used to perform shock testing on the proposed tile for a certain class of submarines. XHT tiles are currently applied during new construction, but there is currently not a mainte... XHT Test Tile will be used to perform shock testing on the proposed tile for a certain class of submarines. XHT tiles are currently applied during new construction, but there is currently not a maintenance tile used for inservice boats. Electric Boat currently procures XHT tiles from Globe Composites and applies them at new construction. However, the maintenance procedure will differ from the methods at new construction, so a slightly thicker tile is needed for the maintenance yards.