The blindfolded man requires 5 turns.

• Open two adjacent holes.
• Open two diagonal holes. Now at least 3 holes are open. If 4th hole is also open, then you are done. If not, the 4th hole is close.
• Check two diagonal holes.
• If one is close, open it and all the holes are open.
• If both are close, open any one hole. Now, two holes are open and two are close. The diagonal holes are in the opposite status i.e. in both the diagonals, one hole is open and one is close.
• Check any two adjacent holes.
• If both are open, close both of them. Now, all holes are close.
• If both are close, open both of them. Now, all holes are open.
• If one is open and one is close, invert them i.e. close the open hole and open the close hole. Now, the diagonal holes are in the same status i.e. two holes in one diagonal are open and in other are close.
• Check any two diagonal holes.
• If both are open, close both of them. Now, all holes are close.