Okay. From: Tim Carey, "Mountjoy: the story of a prison" (Cork: The Collins Press, 2000, 2005).

In March 1942 Behan was in Mountjoy for a few days after his release from borstal in Liverpool. In April he was arrested after a shoot-out with detectives near Glasnevin and sentenced to 14 years; he spent 18 months in the Joy, transferred to Arbour Hill, and released in an amnesty at the end of the War. He was back in Mountjoy twice more: in 1948 for assaulting a Garda and using profane and obscene language and in 1954 for drunk and disorderly. He was one of Governor Kavanagh's favorite prisoners, and Kavanagh arranged fro Behan to meet Sean O'Faolain -- and O'Faolain published Behan's first serious literary effort in "The Bell".

His best known play "The Quare Fellow" is set in Mountjoy at the time of the execution of Bernard Kirwan in 1943....Throughout the play a prisoner in 'the digger' -- the punishment cell -- sings "The Old Triangle".... (pp.228-230)

The triangle (and a bell) was used to signal the times for various functions: at 5:30 a.m. the first bell signaled the warders to assemble and the prisoners to arise: To begin the morning/A warder bawling/"Get up out of bed you/And clean out your cell. Most prisoners were responsible for cleaning their cells prior to starting work for the day -- in their cells in the beginning, about 1850. (p.53)

Hope this helps.