Paneled domes are constructed of separately framed timbers covered in plywood. The three principal timbers included fir, pine, and cedar. Other hollow masts were made from two tapered timbers hollowed and glued together. Ceiling timbers held up the roofs. Infestations are also usually a problem of old wooden houses built with untreated timbers. Finds include flint tools, burnt flint, worked timbers, wooden platforms and pits. Trusses usually occur at regular intervals, linked by longitudinal timbers such as purlins. Sheesham is among the finest cabinet and veneer timbers. Dendrochronology is an important technique especially for dating the timbers of wooden ships. This immediately stimulated the trade in West Indian timbers including, most importantly, mahogany. The Commission found that replacing the decayed deck timbers would be prohibitively expensive. Pierratage or bousillage is the material filled into the structural timbers. Forster pillaged the castle, stripping it of its timbers and furnishings. The external timbers are painted red. They were braced internally with a series of built-up longitudinal timbers called "keelsons".