(row1) Beams formed by 4 or 6 members. The top row is separated from the bottom with bamboo/ wood slats so that the upper bamboos do not slide over the lower. (row2) Central double rafter. Wide range of applications in the construction of bridges & structures for rural facilities. (row3) Lateral double rafter. Each rafters secured independently at the side support & each other. Often used in rural bridges & structures. (row4) Lateral double rafters. Often as central support of bridges/sheds.