| 摘要 |
A spacer maintains a structure in a spaced relationship relative to a mould inner surface surrounding structure and having a mould inner opening impermeably covered by a stretchable sheath. Stretchable sheath engages structure when a retaining force for retaining structure in spaced relationship is applied during introduction of a settable mixture into space to form a product therein. When retaining force is withdrawn, sheath is smoothly aligned with mould inner surface and smoothly bounds space therewith for forming product. By impermeably covering mould inner opening, sheath further prevents flow of settable mixture outside of space there through.
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