The Collaborative International Dictionary
Centering \Cen"ter*ing\, n. (Arch.) Same as Center, n., 6. [Written also centring.]
Wiktionary
n. a type of formwork which serves as a temporary structure during the construction of arches and bridges. vb. (present participle of centre English)
Wikipedia
Centring, centre, centering, or center is a type of falsework: the temporary structure upon which the stones of an arch or vault are laid during construction. Once the arch is complete, it supports itself, but until the keystone is inserted, it has no strength and needs the centring to keep the voussoirs in their correct relative positions. A simple centering without a truss is called a common centering. The cross piece connecting centering frames are called a lag or bolst.
The centring is normally made of wood timbers, which was a relatively straightforward structure in a simple arch or vault, but with more complex shapes, involving double curvature, such as a small dome or the bottle-shaped flues of the kitchens of some Norman-period houses; clay or sand bound by a weak lime mortar mix could be used. The shaping of this sort of centring would probably be done by eye, perhaps with the help of a template and the stone or brick structure laid against it. On bigger work, like a 19th-century commercial pottery kiln, this was impractical. The structure would be built round a post acting as a datum, and each course of stonework would be set at a distance from the datum as measured by a stick or string.
On completion of the intended structure, the centring of whichever sort is removed called "...striking the centering...", and work on pointing and other finishing continued.
Usage examples of "centring".
All thrust was centred in the small of the back, that area on the opposite side of the body's circumference from the hara, the place in the lower belly where all force, all centring energy resides.
Wolf was aware of his body wanting to tense and he fought the instinct, relaxing, remembering, centring while death flashed in at him quickly, more quickly still.
Stakes and cords for laying out foundations, leather thongs and wood for scaffolding, hurdles, timber for centring, lead, glass-and carriage for all these.
The mastercarpenter, who had once been an assistant at Shrewsbury under Master Robert, was beginning the construction of centring for the great west window and the portal.
At three hundred metres she was too far away from Greg, the effect was localized, centring round the gondola.
It is a rather restless, cultureless life, centring round tinned food, Picture Post, the radio and the internal combustion engine.
You can imagine also the petty jealousies centring round the fact that American officers monopolize all the taxis, drink up all the whisky and have inflated the rents of furnished rooms to unheard-of levels.
The truth is, the general effect of the schoolroom, with its scores of young girls, all their eyes naturally centring on him with fixed or furtive glances, was enough to bewilder and confuse a young man like Master Langdon, though he was not destitute of self-possession, as we have already seen.
This he soon found out, and humored her in the fancy that she could exercise a kind of fascination over him, though there were times in which he actually felt an influence he could not understand, an effect of some peculiar expression about her, perhaps, but still centring in those diamond eyes of hers which it made one feel so curiously to look into.
He longed to use its centring influence now but deep, controlled breathing in front of the Director was out of the question.