Those on the picket line are seeking the restoration of the first hour of travel time.
Pickets are placed at construction sites today at Intel in Leixlip, Co Kildare and Pfizer in Grange Castle, Co Dublin.
It is part of a 24-hour strike by mechanical workers at two engineering companies, H A O'Neil and Leo Lynch.
Plumbers, pipefitters and welders, who are members of the Unite trade union, voted in favour of taking industrial action in a dispute over the restoration of a travel allowance.
Those on the picket line are seeking the restoration of the first hour of travel time.
It was originally cut as a so-called "temporary measure" following the 2008 financial crash.
Trade Union Unite says construction workers are "continuing to shoulder the burden of austerity-era pay cuts during an unprecedented cost-of-living crisis."

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