Leaning boards ( also called Slant boards) were invented for Hollywood players to relax between takes. Hollywood costumes were frequently cut on-the-bias, and tailored so snugly that the actor could not sit without bursting a ladder of seams. In fact, most of the time, there were no zippers or buttons on the costumes. Actors were stitched into their garments.
When you see Jean Harlow in Dinner at Eight, and marvel at the impeccable fit of the famous white silk gown, be aware that Harlow’s mobility was severely limited. In fact, just breathing was something of a chore.
Remember, classic Hollywood movies were designed to project images of glamour. For the screen, costumes had to be photogenic. Comfort and practicality were of little concern.
These days, leaning boards are still in use, but they are the exception rather than the rule, for a variety of reasons. Modern fabrics are more forgiving. It is also quite rare for a costume to be designed, cut and sewn, for one actress. Most costumes are off the rack, and modified. Besides, in today’s Hollywood, stars who receive multiple millions for one film are loathe to suffer the indignities of such a tight fit.