Making track
 

This not only shows part of the production process for making Carrier track... it's also fairly unique in the AWM database in that it also shows the thumb of the person copying the photograph! ;)

Description:
ID Number: 011873
Physical description: Black & white
Summary: 1942-03-26. NEWPORT. TRAWLER TRACKS FOR THE BREN GUN CARRIER. CASTINGS FOR THE TRACK LINKS HAVE THEIR CORED HOLES REAMED TO SIZE ON A VERTICAL ARCHDALE DRILL. (NEGATIVE BY CRANSTONE).
Copyright: clear

Also the term "Trawler" has been applied by someone with more of a nautical than military machinery background... There are several other pics in this series which you can find by doing a search...