The expression "sleep tight" had its origins in the times when bed frames had a knotted rope grid to support a mattress pad. In order to sleep well it was important to keep the rope grid as tightly stretched as possible.
The legs of the doll figure in this picture were made to wrap around the rope which allowed tightening of the grid and making for a better night's sleep. The cradle could hold the doll for play or until its next use.
