In a safe crib, the hardware — bolts, screws, and the like — should be firmly secured, with no sharp edges or rough areas and no spots that can pinch or otherwise injure your child
Cry it out simply refers to any sleep-training approach that says it's fine to let a baby cry for a specified, usually short, period of time before offering comfort.
SIDS- is the unexpected death of a child under age 1 in which an autopsy does not show an explainable cause of death.