Do not cover a resting cat in a way that traps it, restricts breathing or prevents it moving away. Some cats choose to burrow under light bedding, while others prefer an uncovered surface. Let the individual decide and avoid heavy blankets or overheating. During transport, a light cover over part of a carrier may reduce visual stimulation for some cats, but ventilation must remain clear and the carrier must not become too warm. That is different from wrapping the cat tightly for ordinary comfort.
Handling techniques used by trained veterinary staff should not be improvised as a way to force affection or control. If the cat is unwell, chilled or needs specific care, ask your vet what is appropriate. Comfortable bedding should offer a choice and support rest, not become a restraint the cat cannot escape. Check the cat's ability to leave the bedding without assistance; a blanket tucked around the edges can restrict choice even when the material feels light.
For product comparisons alongside this advice, see Velvet Nest and Silver Velvet Nest. The details below explain their sizes and uses.
Further reading: cats.org.uk; pdsa.org.uk; cats.org.uk.
Velvet Nest
Silver Velvet Nest
AeroMat Chill Pad