KnockboyKnockboy is a 706-metre-high mountain on the border between counties Cork and Kerry in Ireland.GeographyKnockboy is the highest peak in the Shehy Mountains and the highest mountain in County Cork with its summit shared with County Kerry. It is the 104th highest peak in Ireland.GeologyThe mountain is composed of sandstone laid down in the Devonian period which was subsequently uplifted to form a mountain range, before being eroded into its present form by glaciers during the last ice age.