Setting Out Plants From the "Flat"
When the seedlings are sufficiently hardened, if the weather is suitable, they are transplanted into the open garden. The "flats" are taken into the garden, so that the transfer may be made directly and with the least possible damage to the roots of the plant. An ordinary trowel is the best implement for transplanting most seedlings.
This image is from: Luther Burbank: his methods and discoveries and their practical application. Volume 3 Chapter 4