The ancestral rig was the mastless triangular crab claw sail which had two booms that could be tilted to the wind. These were built in the double-canoe configuration or had a single outrigger on the windward side. In Island Southeast Asia, these developed into double outriggers on each side that provided greater stability. The triangular crab claw sails also later developed into square or rectangular tanja sails, which like crab claw sails, had distinctive booms spanning the upper and lower edges. Fixed masts also developed later in both Southeast Asia (usually as bipod or tripod masts) and Oceania. Austronesians traditionally made their sails from woven mats of the resilient and salt-resistant pandanus leaves. These sails allowed Austronesians to embark on long-distance voyaging. In some cases, however, they were one-way voyages. The failure of pandanus to establish populations in Rapa Nui and New Zealand is believed to have isolated their settlements from the rest of Polynesia.