Sorry, Charles and Pete,
     that I didn't do a very good job of describing it; so let me try again=
..   A picture would be 'worth a thousand words', but I don't want to go the=
re unless we have to.
Each of the four strips is formed to exist in an unloaded shape like I ment=
ioned-approximately one cycle of a cosine.  After shaping all four strips t=
o be identical, they are then welded or glued together at their ends in pai=
rs, yielding two identical spring components.  There are two ways a strip p=
air could be welded at their ends, one being with a strip lying on top of a=
nother, so the pair are in contact virtually everywhere.  That is not the c=
hoice used.  Rather from that starting arrangement, flip one of the two so =
that when they come together, they touch only at their ends, where they are=
 then welded.  Each end of these two identical components (four ends total)=
 will look kinda like what you would see from the 'sharp' side only if you =
were to imagine a plane passing through the center of a water drop about to=
 break away from the spigot.
If you can visualize their shape, then now take one of these two welded str=
uctures and insert it inside the other one at right angles until their cent=
ers meet.  The insertion will meet a resistance force only as the pair appr=
oach their final resting place.  There, with the planes of the two componen=
ts resting at right angles to each other, is realized the 4-fold rotational=
 symmetry I mentioned.  In other words, visualize an axis that passes throu=
gh the centers of both the top union and the bottom union.  For any rotatio=
n of the set about this axis, if the angle is 90 degrees, the spring will l=
ook the same from a fixed position of view.  In solid state physics we call=
 this a 4-fold rotational symmetry, because 4 such indistinguishable rotati=
ons bring it back to where you started.
     The l
Sorry, Charles a=
nd Pete,
     that I=
 didn’t do a very good job of describing it; so let me try again.&nbs=
p;  A picture would be ‘worth a thousand words’, but I don=
’t want to go there unless we have to.
Each of the four strips is formed to exist in an unloaded shape like I=
 mentioned—approximately one cycle of a cosine.  After shaping a=
ll four strips to be identical, they are then welded or glued together at t=
heir ends in pairs, yielding two identical spring components.  There a=
re two ways a strip pair could be welded at their ends, one being with a st=
rip lying on top of another, so the pair are in contact virtually everywher=
e.  That is not the choice used.  Rather from that starting arran=
gement, flip one of the two so that when they come together, they touch onl=
y at their ends, where they are then welded.  Each end of these two id=
entical components (four ends total) will look kinda like what you would se=
e from the ‘sharp’ side only if you were to imagine a plane pas=
sing through the center of a water drop about to break away from the spigot=
..  
If you can visualize their shap=
e, then now take one of these two welded structures and insert it inside th=
e other one at right angles until their centers meet.  The insertion w=
ill meet a resistance force only as the pair approach their final resting p=
lace.  There, with the planes of the two components resting at right a=
ngles to each other, is realized the 4-fold rotational symmetry I mentioned=
..  In other words, visualize an axis that passes through the centers o=
f both the top union and the bottom union.  For any rotation of the se=
t about this axis, if the angle is 90 degrees, the spring will look the sam=
e from a fixed position of view.  In solid state physics we call this =
a 4-fold rotational symmetry, because 4 such indistinguishable rotations br=
ing it back to where you started. 
 =
;    The l
=