What's on display : breasts
Why it works : These are, for the most part, guarded positions. Depending on how high the shoulders and hands are raised, they serve either to obscure or frame the bosom. Models with pendulous, u-shaped breasts will often hoist them up in such a fashion to de-emphasize the drooping effects of gravity, or any cosmetic scarring on the undersides (obviously not a concern in the pinup world).
What's important : Bosom heaves and is squashed. One or both arms make contact with the ribcage and each other. Particular attention is to be paid to overlaps. Flesh is pinched in and pooched out at all contact points, particularly with a voluptuous model.
Mood Implications : Different postures, head positions and facial expressions accompanying these actions indicate different emotional states -- pride, indigence, squeamishness, shyness, boredom, patience or impatience. Add to this the physical state of being cold.