The Amalgamated Society of Boilermakers, Shipwrights, Blacksmiths and Structural Workers (ASB) was a trade union in the United Kingdom.

Many of its members worked in shipbuilding, in which industry it was the leading trade union, while over time it also developed strength in engineering and construction.

Initially, these branches operated almost entirely independently, but from 1842, under new secretary John Roberts, it began introducing national controls on spending and reserves, and ran an annual delegate meeting.

This, coupled with concerns about the rights of striking members and those who were locked-out, led it to join the United Kingdom Alliance of Organised Trades.

This confederation achieved little, but the Boilermakers retained its interest in such an organisation, and so in 1870 it joined the recently-formed Trades Union Congress (TUC).

[3] Criticisms of Knight's leadership mounted during the 1890s, as he was seen as increasingly conservative, opposed to socialism and trade unions of unskilled workers.

Upset by the increasing role of general and industrial unions at the TUC, he won a vote to disaffiliate in 1894, but it reaffiliated the following year.

Cummings led the union into membership of the Labour Representation Committee, and at the 1906 UK general election, it sponsored James Conley as a candidate, and also paid half the expenses of member John Hill.