Provide students with familiar shapes drawn on or cut out of a sheet of paper and have them determine whether a line crossing the image is a line of symmetry. Simple hearts, pyramids, diamonds and faces all work as shapes. Place or fold the line at the center of these shapes for some examples and off-center on others to create some images with a line of symmetry and some without, and ask students to determine which have a line of symmetry and which do not.
Use the familiar method of cutting a snowflake out of a folded piece of paper to illustrate the concept of lines of symmetry. Have students fold a piece of paper in half and then in half again and cut shapes out of it to create a snowflake. Unfold the paper and describe how folding the paper before cutting it created the lines of symmetry.
Have students identify lines of symmetry in nature. Leaves, flowers, insects, fruit and seashells all demonstrate symmetry, but the possibilities are endless. Students can mark the line of symmetry using markers, tape or by folding the things that they find. Students can then glue or otherwise fasten these items to construction paper to display their comprehension.
Have students identify lines of symmetry in the capital letters of the alphabet. Depending on the type of font that is used, there are only a handful of letters in the alphabet that do not have a line of symmetry. Challenge students to locate these letters to demonstrate the concept of symmetry. This can be expanded even further by having students create words that display a line of symmetry, like TOOT, which has vertical symmetry, or ICEBOX, which has horizontal symmetry.
Illustrate the concept of symmetry by providing students with handheld mirrors that have a straight edge. Students can hold the mirror up to any object and observe how the edge of the mirror creates a line of symmetry for whatever it is held up against. This activity is especially interesting when used on objects that appear to be symmetrical, but really aren't, such as the human face. Hold the mirror at an angle against your face and observe in another mirror how different your appearance becomes when your face is completely symmetrical.