Flip one paper plate over and draw two intersecting perpendicular lines that form a cross with the ruler and marker. Label this cross with the four directions North, South, East and West using a compass for clarification and accuracy.
Make a hole at the center point of the plate where the lines intersect with the scissors.
Draw two intersecting perpendicular lines using the ruler and marker on the top of the second paper plate to find the center point.
Lay out a small pile of the clay at the second center point you just found. Line the outside edge of the clay with some small stones.
Insert the end of the pencil without the eraser directly into the pile of clay. Push the other end of the pencil through the plate with the hole so the plate sits upside down on top of the base plate. Tape the entire edge of the first plate to the edge of the second plate.
Trace two triangles that measure an inch on each side on the poster board using the ruler and marker. Cut out the triangles with the scissors.
Cut slits in both ends of the straw with scissors. Push the triangles into the slits and secure them in place with the tape.
Measure the straw with the ruler. Find and mark its center. Push the pin completely through this point of the straw and push the remainder of the pin into the eraser.
Place the wind vane on a sturdy and flat surface above ground level outdoors. Use the compass to verify that the marked "North" on the wind vane correlates with the actual direction on the compass. Calculate the direction of the wind.