| 摘要 |
<p>The spiral staircase has steps screwed to a continuous storey-high centre column using bolts (12, 13) passing through holes in the column. All the holes are sited only on the side of the column where the step (11) fits against it. Adjacent to the bolt holes are apertures with a dia. exceeding that of the screw head (12a, 13a). Their diameter may be twice that of the bolt holes, and it may be between two of the latter, at the same height.</p> |
