Step 1: Stretch each strip of bacon and cut it crosswise into 4 pieces—each should be large enough to go around a prune. Cut the cheese into 1/4 by 1/4 by 1-inch pieces and stuff them inside the prunes.
Step 2: Wrap each prune in bacon and secure with a bamboo skewer or toothpick inserted through the side—leave a handle to resemble a hammer. The hammers can be prepared several hours ahead to this stage.
Step 3: Set up your grill for direct grilling and preheat to high. Brush and oil the grill grate.
Step 4: Arrange the prunes on the grate, placing a skewer shield or folded foil under the exposed portion of the skewers to keep them from burning. Grill the hammers, turning with tongs, until the bacon is crisp and the cheese is melted, 1 to 3 minutes per side. Transfer to a platter and serve hot.