Trimming selected areas of embedments for electron microscopy--dead simple.

Precision trimming of specific areas of plastic embedments can be accomplished without having to find the specimen detail in the block face itself. The desired area is located in a thick section of the pretrimmed block. The position of the area in the section is evaluated using an ocular micrometer. The block is then mechanically trimmed in the ultramicrotome in such a way that the amount of plastic removed from each of its sides is determined from the magnitude of the knife advance. The procedure can be used in connection with inclined blocks if the microtome head can be rotated behind the specimen orientation arc.