When turning an immobile bedridden client without assistance, which action by the nurse best ensures client safety?

When turning an immobile bedridden client without assistance, the best action to ensure client safety is to put bed rails up on the side of the bed opposite from the nurse. This is important because the nurse can only stand on one side of the bed, so having bed rails on the opposite side prevents the client from falling out of bed. Option A, which suggests securely grasping the client's arm and leg, can potentially cause client injury to the skin or joints. Options C and D, correctly positioning and using a turn sheet, and lowering the head of the client's bed slowly, respectively, are useful techniques during client turning but are of lower priority in terms of safety compared to the use of bed rails.