求翻译：　　双层床床架与护栏底部间距不大于89毫米，而角护栏，应至少比床垫高127毫米以上，以防孩子滚落下去，还应选购两侧都有护栏的，为保安全，以防万一。是什么意思？

　　Bunk bed frame and guard rail bottom spaced not more than 89 mm, and point guard rail, than Block up the bed more than 127 mm at least, prevent child tumbled down, should also purchase fence on both sides, for safety, just in case.