Wooden crosses for church walls are used in worship spaces associated with many different denominations. The cross is usually facing the congregation and is behind the podium where the sermon is given. In part, this is to remind the congregation of what the cross represents. Crosses are usually made out of wood, and are typically also very large. You can choose to make your cross from a variety of different woods, but cedar is often a good choice because of how lightweight it is.
Measure 26 inches from one end of your 90-inch board. Make a 2 1/2-inch deep cut perpendicularly across the board.
Make another 2 1/2-inch deep cut that is parallel with the first, and 5 inches away from it. Knock out this piece of wood using your hammer and chisel so you have a 5-by-5-inch notch that is 2 1/2-inches deep in the board.
Measure 17 1/2 inches away from the edge of the 40-inch board, and make a 2 1/2-inch deep cut perpendicularly across it. Measure 17 1/2 inches away from the opposite end and make another 2 1/2-inch deep cut that is parallel with the first. Knock out this section of wood just as you did in the last step so that the notches on both boards are equal.
Position the boards perpendicular to each other, and line the notches up. This is your cross. Screw through the shorter arm into the longer one using 3-inch screws.
Turn the cross over so that the screws are not visible. Drill two 1/8-inch holes through each board. Each hole should be 4 inches away from each end. Drill a 1/2-inch hole that is 3-inches deep in each of the 1/8-inch holes. These holes will hide your screw heads once you have mounted the cross to the wall.
Find studs in the wall using your stud finder. Position the cross against the wall using your level to ensure that it is level. Screw through 1/8-inch holes using your 6-inch screws and tap 1/2-inch dowels into the 1/2-inch holes using your hammer.
Always use caution when using drills, saws, and other powered carpentry tools. Always wear protective eyewear, and keep young children away.