In some jurisdictions, every wall will have a horizontal 2x4 about half-way down the wall. Drilling through the top-plate will get you started, but you'll need

In some jurisdictions, every wall will have a horizontal 2x4 about half-way down the wall. Drilling through the top-plate will get you started, but you'll need a special 4' long drill-bit to make the second hole you need in that 2x4. It's kind of fun to drill with such a long bit.