This paper mainly expounds the characteristics of hand-in-hand mode.

1. Form and characteristics of hand-in-hand model: two equilateral triangles or isosceles right triangles or two squares have the same endpoints. Two identical graphs with a common vertex and two adjacent edges equal.

2, hand identification: judging the left and right: put the vertex of the isosceles triangle up, facing the reader, the reader's left hand vertex, right hand vertex.

3. Definition of congruent hand-in-hand model: Definition: a figure formed by two isosceles triangles with the same vertex angle and the same vertex. Left hand pulls left hand, right hand pulls right hand.