It just means he is on holiday/vacation for a block of time - a week/fortnight (two weeks)/month etc rather than just one or two days.

This term actually has more meaning, since usually people don't really need to differentiate "leave" (vacation) from "block leave". This term came into prominence when the financial industry had rogue traders that were performing unauthorized trading, sometimes gambling ever larger amounts in order to recoup prior losses so they won't be discovered for the initial unauthorized trades. In this area, it refers to a block (usually one week) where the employee is on leave and completely separated from the company's computer systems and communication devices. The thinking is that if any of this unauthorized trading is occurring, it would come to light during such absences with no access to the systems.

This refers to annual leave taken in a block of time, e.g. one week or more, to provide staff with a period of extended rest and refreshment. Sabbatical Leave and Career Break Leave are examples of Block Leave.

Carina, what was after 'and back on'? I mean, was it a time, or a day? My first idea was that it would be an obliged pause time, obliged lunch time. But probably Deb and GuideDogSaint know it better.

It means the person is away for perhaps a week or more...it refers to a block (chunk) of time.