The Sahatavaran Lujuuslajitteluyhdistys (SLLY) was founded in January 1964 after the first strength grading course, led by professor F.E. Siimes. It has trained more than 4,500 visual strength graders on over 350 courses and keeps a register of the stamp codes of the people it has trained.
Since 1998 the training has followed the Nordic INSTA 142 standard. The strength classes align with European EN 338 classes: T3=C30, T2=C24, T1=C18 and T0=C14. The association acts as a contact organisation for those holding grading authorisation, and sells a book for its 50th anniversary.
Have you taken one of the association's courses? Share your experience in the comments for other professionals.
