Vault (mathematics)

In geometry, the Steinmetz solid is the solid body generated by the intersection of two or three cylinders of equal radius at right angles. It is named after Charles Proteus Steinmetz, though these solids were known long before Steinmetz studied them.If two cylinders are intersected, then it is called a bicylinder or mouhefanggai (Chinese for two square umbrellas [1], written in Chinese as 牟合方蓋). If three cylinders are intersected, then it is called a tricylinder.
See more at Wikipedia.org...