Dear Satish,
You can engage security guards at your construction sites on contract basis through private security agencies. This arrangement would be coming under the purview of the Contract Labor (Regulation and Abolition) Act,1970. The applicability of the Act and other statutory requirements like registration, licensing etc., depends on the no of contract security guards to be engaged and the duration of the construction projects. First, you go through the provisions of the said Act and the Rules framed under it. Then, you engage the services of a labor law consultant in the locality who will guide you in the preliminary works in this regard.