Slats in either the horizontal or vertical direction are permanently fixed to the back of the panel, whilst the secondary perpendicular slats remain loose, held solely in place by the upper row.
This allows for a degree of movement in the panel, which may warp, subject to changing levels of dampness and atmospheric pressure.
It is an interventive procedure which may involve sanding the back of the panel in order to create a flat surface to affix the cradling.
It is a non reversible procedure which alters the condition and state of a work of art, which triggers ethical issues.
Nowadays, in the modern world of conservation cradling a painting has been outdated and subject to criticism.