Abstract: A block is disclosed which comprises an upper frame portion and a lower leg portion that are integrally formed under the condition that the leg portion fits into the frame portion. The frame portion can be fitted to the bottom portion of a PET bottle and removed from it, the periphery of the frame portion being provided with coupling means that couple together adjacent blocks. The leg portion includes at a center portion thereof a receiving hole into and from which the top portion of a PET bottle is fitted and from which it is removed, the outside of the receiving hole being provided with gaps within which are sandwiched corresponding peripheral walls of the frame portions coupled together by the coupling means.