  We clarify the relation between orbifold and interval pictures in 5d brane
worlds. We establish this correspondence for Z_2-even and Z_2-odd orbifold
fields. In the interval picture Gibbons-Hawking terms are necessary to fulfill
consistency conditions. We show how the brane world consistency conditions
arise in the interval picture. We apply the procedure to the situation where
the transverse dimension is terminated by naked singularities. In particular,
we find the boundary terms needed when the naive vacuum action is infinite.
