1. Wedges are best used to fix these kinds of leaks, which can occur in either head or side staves. The first step is to use a scrapper to uncover the source of the leak (important if wine is obscuring the surface).
2. Next, and most important, determine the direction of the grain. This is a side view of a stave where the grain is at an angle. The two lines on either side represent entry and exit of the grain leak. "X" marks the spot where the grain leak surfaces. The black line on the face of the stave indicates where the wedge must be placed to stop this leak. Angle of grain ascent determines this.
3. Then use a sharp-bladed chisel to make a hole BEFORE the grain exits. The wood chisel needs to cut ACROSS the grain where the wine is seeping, never lengthwise (this would aggravate the problem).
4. Cut the wedge width to the proper size and insert it into the hole you have made. Gently tap it into position; the wedge should fit snuggly.
5. Use the wood chisel to cut off the excess wedge portion, with the back side of the blade up to make a nice cut. Please note that if the blade of the chisel is dull, you will simply pull out the wedge instead of making a clean cut. Done!