Painting 23B shows a pilot apparently preparing to eat. The waist belt will keep him close to the restraint bar, allowing him to devote his full attention to his meal packet instead of wasting effort countering Newton’s third law.
The content of this painting is confusing. The man is clearly restrained by the orange-colored belt to the cross-bar. He appears to be opening a food packet with his hands. But his posture is counter-intuitive for weightlessness: continuous flexing of the waist and knees without gravity's assistance is rapidly fatiguing (although that was not widely appreciated so early in the space age). Likewise, unrestrained, his feet would slip outwards, and if restrained, would push him upward behind the bar.
Originally, I thought this was an illustration of a rowing machine-type exercise device, with the man donning and adjusting workout gloves instead of opening a meal packet. But there are no pivots or sliding elements or foot restraints--no moving parts at all.