Twin-strip technique

Crossposition for Twin-strips of {4} and {3}
   

         The T-strip technique is a variation of P-strip technique called “twin-strip” or “T-strip” technique (Frederickson, 1997). In P-strips, we cut a figure into pieces that rearranged to form a repeating element that fills out a strip. But in T-strip, there are two equally elements placed symmetrically about a center point and they fill out a plain strip by the pairs of twined elements. This center point usually lies on the middle of their boundary. Frederickson (1997) called such a point an anchor point.

Such a strip also can be used to derive a dissection, but we cannot translate the strip superposed on it as freely as on a P-strip. We have two ways to crosspose these strips. One of which is to crosspose the edge of one strip passing through the anchor point of second strip. The other way is to crosspose the second T-strip over the first strip with their anchor points coincident with each other.

        When a P-strip and a T-strip are used, Lindgren called this a PT dissection (Lindgren, 1972). When two strips were T-strips, he called it a TT dissection. Since the twined strip composed of two equally elements that each rotated 180 degrees around the anchor point to match with the other one, such elements can be hinged during the transformation.
　

　

TT dissections

        In a TT dissection, both strips are twin-strips and the superposition has been restricted that one T-strip must superposes the other strip with their anchor point coincide. 

 {4} to {3} {4}
{6} to {3} (5)
 
 
  
 PT dissection

      A PT dissection is composed of the superposition of  a P-strip over a T-strip. The P-strips must pass through the anchor points of the T-strips.
{5} to {3} (6) 
　
　

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