DCHP-1 Online
boom timber 
See quote.
- 1883 The first business of the drive is to collect all these scattered timbers, and "boom" them into the main channel of the river, that is, confine them there by long half-square logs called "boom timber," fastened at the ends by "boom chains."
- 1883 The first business of the drive is to collect all these scattered timbers, and "boom" them into the main channel of the river, that is, confine them there by long half-square logs called "boom timber," fastened at the ends by "boom chains."