The crop produce from these plantations were generally exported to other countries from Singapore with the assistance of Chinese merchants based in that city. From the 1860s onwards, many of these Kangchu chalked up debts and began to sell their property rights to these merchants or to larger business magnates ("Kongsi" in Teochew) based in Singapore, who were known to the locals as "Tuan Sungai" (literally Masters of the River). The Kangchu then were often hired as supervisors or managers by the merchants to keep watch on the day-to-day operations of the gambier and pepper plantations. Temenggong Abu Bakar began to issue contract-style letters of recognition to these Kangchu; the letters were known by their Malay name "Surat Tauliah".