1) The vertical timbers in a building or other construction were referred to as posts.
1433 In diversis peciis meremii ... vj duble postis, vj thoregistes, York
1498 with axis hewid in sonder the postez of the hous and pulled it downe, Wilstrop
1509 I will that the Chappelle … in Estburne be beylded … of viij postes
1521 a kilnehouse of x postes that lieth in the laithe, Pontefract
1570 one baye of a laythe containing fouer postes, Falhouse. The verb to post was usually to prepare timber for use as posts: 1312-3 Pro meremio prosternendo, postando et sarrando ad grangiam, Ryther
1418-9 In expensis iiij carpentariorum postantium easdem quercus 3s 4d, York
c.1520 Will’mo Howyd posting tymber for the said fertter per iij dies and sawyng 18d, Ripon
1570-80 For posting and squarynge syplinges for the mason’s scaffaldes 16d, York
1580 maye … cutt downe, fell, post, breake and carye awaye the same trees, Thurstonland
1707 paid for timber … paid for posting it, North Bierley. It could also refer to setting up the ‘posts’ in the new building: 1561 I postyd new my lathe [barn], Woodsome.
2) A section of coal left unworked in order to support the roof of a colliery, an alternative to pillar.
The first example given here may be early evidence of the post and stall method of working: 1486 with poste and thyrle, Cortworth
1704 paid for 2 dayes in a post, Farnley
1714 there must be care taken … that there be sufficient strong posts, Shibden. The term ‘post and stall’ is in the OED from 1839 but it has not been found in early documents. It describes the method of working coal in which ‘posts’ of coal were left uncut and the coal-getters worked in the spaces or ‘stalls’ between them. The practice in some parts of Yorkshire goes back to the fifteenth century at least.