# Meshing rules and meshing rules

Hello there,
Some rules must be fulfilled before a geometry is meshable (see mesh). For linear
elements (ie. qu4 or he8), the sum of all divisions (see div) of each surface must
be even. In case of quadratic elements (ie. qu8 or he20) this sum must be
divisible by 4 without residue. Opposite edges of a given surface might have
different divisions. For example on the left side of a given surface the division
is 8 and on the right side it is only 4. But only two opposite surfaces of a body
can use this feature. These surfaces are called top and bottom surfaces. These surfaces are called top and bottom surfaces. All other surfaces of this body must have unique divisions on opposite edges. In
case of 3 sided surfaces it is necessary to apply a minimum division sufficient for two elements along the edge.

â€śOpposite edges of a given surface might have different divisions.â€ť how is it realized?
â€śFor example on the left side of a given surface the division is 8 and on the right side it is only 4.â€ť how is that?
â€śBut only two opposite surfaces of a body can use this feature.â€ť what bodies?
â€śAll other surfaces of this body must have unique divisions on opposite edges. In
case of 3 sided surfaces it is necessary to apply a minimum division sufficient for two elements along the edge.â€ť may you provide me with an example on the matter?
regards

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