How to write a circular to Office boys for keeping and submitting record of over time work details and reason for over time?

Dear All,
My office timings are 9.00 am to 17.30 pm, Please guide me how to write circular for all workers(electrician/pantry boys/office boys) shall maintain and keep the record of works performed during over time. Company pays for over time, so HR must have the record of work details during over time and reason for over time.

Dear Richa,
Office boys are placed at the lowest rung of the hierarchy. When they work, whether during regular working hours or after that, is under the instructions of their Manager or HODs. Therefore, their overtime (OT) is required to be explained by the Manager or HOD. Office boys are hired especially for physical work. They may not maintain properly records of even their own work.
At the security, a separate OT Register may be maintained. While going off from duty, they can record their details and this extra working hours may be validated by the respective HOD on the next day. This way, you will come to know for which department the OT should be attributed.
Thanks,
Dinesh Divekar

Dear Sir,
The office boys work under their assigned reporting manager. The RM wants the HR to create a circular for their OT in which work details shall be their.
Kindly, provide some format of circular for the same.