Terry’s Locksmiths offer sales, installations and repairs of letterbox locks across the Gold Coast. Call (07) 5601 1820 or visit our showroom at Burleigh Heads or Southport. At Terry’s Locksmiths we supply and install letterbox locks across the Gold Coast. There is a very common letterbox lock called lock focus that come in five different sizes. This brand and among other brands we also stock will fit in almost any letterbox, you just need to measure the size. The five sizes are 11mm, 16mm, 19mm, 22mm and 32 mm long.