European grading rules for sawn poplar

  Knots Shakes Heart traces Wane Rot or dote
Grade 1
A piece is classified as grade 1 when both sides are grade 1 or when one side is grade 1 and the opposite side is grade 2
Sound knots are excluded except if smaller than 8 mm Edge shakes not exceeding 30 mm are permitted on each extremity Excluded Excluded They are excluded, as well as damages due to insects
Grade 2
A piece is classified as grade 2 when both sides are grade 2 or when one side is grade 2 and the opposite side is grade 3
Small or medium sized, in limited number.
Rotten or non-intergrown knots are excluded.
Edge shakes not exceeding 30 mm are permitted on each extremity Admitted if straight Admitted on 25% of the length but limited in width and thickness They are excluded, as well as damages due to insects
Grade 3
A piece is classified as grade 3 when both sides are grade 3 or when one side is grade 3 and the opposite side is grade 4
Medium sized in limited number.
Rotten or non-intergrown knots are excluded.
Edge shakes not exceeding 30 mm are permitted on each extremity Admitted Admitted on 25% of the length but limited in width and thickness Traces of rot are permitted.
Pin holes and other insect damages are excluded.
Grade 4
A piece is classified as grade 4 when both sides are grade 4
Knots size must be limited to 1/3 of the width of the piece.
Rotten or non-intergrown knots are excluded.
Edge shakes not exceeding 50 mm are permitted on each extremity Admitted without limitation Admitted on 25% of the length but limited in width and thickness Rot permitted.
Pin holes and damages due to insects are excluded, except for non-active galeries.

Reference:
 
Project of European Norm EN 975-2 "Sawn timber - Appearance grading of hardwoods - Part 2 (poplar)" (see http://www.cenorm.be/ - Work Programme CEN/TC 175) proposed by the CTBA (http://www.ctba.fr)