This chapter explores frontiers as political and economic constructs, focusing on the contested borders and boundaries of Timor-Leste. At its centre is a dispute about the maritime boundary between Timor-Leste and Australia in which access to petroleum resources in the Timor Sea has been at stake. In 2018, Timor-Leste and Australia signed a Treaty ‘to settle finally their maritime boundaries in the Timor Sea’. Despite considerable mutual self-congratulation, this treaty does not finalise the boundary now (instead creating an anomalous and temporary enclave to accommodate Australia’s economic interests). Nor does it deal conclusively with the crucial question of who should extract oil and gas or where it should be processed: it could not do so, for these decisions are ultimately not for nation states but for international corporations. To them, frontiers are less about pride and security than about opportunities and obstacles. The maritime boundary dispute can only be properly understood in the broader context of relations between Australia, Timor-Leste, and Indonesia. This leads to a border, the division of the island of Timor between Indonesia and (what is now) the Democratic Republic of Timor-Leste. This complex border – one line dividing the island from north to south and another enclosing a small enclave in north-west Timor – is a legacy of colonial occupation by the Dutch in the west and by the Portuguese in the east. For the last quarter of the twentieth century, this border became merely a division between two Indonesian provinces. Soon after East Timor declared independence in the wake of its 1975 abandonment by post-colonial Portugal, Indonesia invaded, uniting the island until a heroic resistance movement led to multinational intervention in 1999 and restoration of independence – and the border. Frontiers are of variable tangibility. Land borders are usually identifiable and impact upon lived space. Maritime boundaries are nebulous and distant: they are the product of complex interactions involving physical features as well as legal and political compromises. They may differ in regard to the seabed and the water column above it. Even more amorphous are economic borders, established by trade or resource-sharing agreements. Then come the least distinct borders between truth and lies, between expediency and principle, between the past and the future, between cynicism and integrity, and between people whose lives count and those whose lives do not. In exploiting the uncertainty of maritime boundaries, Australia trod an unsteady path along the borders of the final type. Public opinion, in-country action and NGO activity have often contrasted with political deceit, arrogance and opportunism.