The male civilian internees' regulations (prepared by the internees themselves) stated that ""Any persons who are not performing some useful work in war-time are failing in their moral obligation. Internees should therefore do their best to do such work as ... agriculture, farming, and stock-breeding, in order to increase the supply of foodstuffs to the camp."" Some male civilian internees chose to cultivate land around their compound in order to become self-supporting; however, the other work imposed on them meant that they never cultivated the land to its full effect. Some refused to carry out this work, even though it was for the common good. Work included wood-gathering parties, latrine duties, working as cookhouse staff and medical orderlies. Sundays were a rest day, but these were later cut to one in every three weeks. POWs and male civilian internees were forced to work as stevedores and in timber yards at Kuching harbour on the Sarawak River and from October 1942, on the extension of the two runways at the Batu Tujoh landing ground to the south of Kuching, where a small sub-camp was constructed. Another sub-camp was made at Dahan, where the Japanese re-opened an old mercury mine, and used POWs to construct access roads. Such work was prohibited by the 1907 Hague Convention, to which Japan was a signatory. Although it was against international law to force the prisoners to work on projects with a military objective, they were informed that refusal to work on these projects would result in their execution. Other forced labour included refuelling the Zero fighters that used the runways; however, this happened only once as the men sabotaged the operation by adding urine and water to the fuel. The work party men were paid in what the prisoners called "camp dollars", the printed paper currency introduced by the Japanese administration. This currency was known colloquially as "banana money" because of the banana trees pictured on the 10 dollar notes. At one point the rate was 25 cents a day for officers and NCOs and 10 cents a day for other ranks. As time went on, the working parties became smaller, as there was a lack of available men due to sickness and death. The women were at first allowed to undertake domestic tasks around their compound; later they were forced to undertake work for the Japanese such as mending uniforms, for which they were also paid in camp dollars. In the later part of the war, when the food shortages had become critical, all internees, male and female, were also used as agricultural labourers on the land around the camp, to produce food for their Japanese captors.