This is something which will not be practise during normal training. Kyek Pa (Breaking Test) should show the precision and power of a technique. If the wooden board breaks, the technique was done with enough precision and power. Kyek Pa is only practised during examination, and sometimes during demonstrations.
Normally boards of pine or spruce (3cm x 30cm x 30cm) will be used, sometimes (ladys handtechnique or youth people) 2 - 2.5 cm thick boards.