Nothing metaphorical here as the Irish took refuge from the marauding Norwegians in these towers. They climbed up by a ladder and pulled it in after them, hoping and praying for the best...
O Key of David, and Scepter of the house of Israel, you open and no one can shut, you shut and no one can open: Come and bring the captives out of the prison house, those who sit in darkness and the shadow of death.