How to find the center of anything without a ruler

The center of an object can be found with a string.

=Needed parts=
 * string
 * any straight edge object

=Straight Object=
 * 1) Take a string
 * 2) stretch the string the full length
 * 3) fold the string in half
 * 4) stretch the folded string
 * 5) it will stretch to the center

=Square or Rectangle=
 * 1) Use a straight object
 * 2) put the straight object across the two opposite corners
 * 3) draw a faint line
 * 4) Do the same of the opposite corners
 * 5) the intersection of the lines is the center

=Any flat object=
 * 1) hold any point on the edge of the object
 * 2) let the object dangle with gravity
 * 3) dangle a string with a weight from the point where it is held
 * 4) draw a faint line along the strings path
 * 5) hold another edge in about 1/4 of a rotation
 * 6) Do the same with the string and mark.
 * 7) The point of the lines intersection is the center of the object.

=Any flat long object=
 * 1) This will find the center of mass for lightweight skinny objects, like a broomstick.
 * 2) Balance the object horizontally on the top of both index fingers, with your hands held apart about, palms facing inwards.
 * 3) Slowly bring your hands together, allow the object to gently slide across your fingers.
 * 4) Your hands will come together under the object's center of mass.

From HowTo Wiki, a Wikia wiki.