Acrylic Matrices are attractive clear plastic blocks with brain shaped cavities oriented in skull flat plane. These are available in different models to accommodate different sizes of rat or mouse brain, and with slots either coronal or sagittal relative to brain. The precision machined slots spaced every 2 mm fit a razor blade or monofilament to make a first cut through the brain, which is visible in the block. This improves over hand cutting for putting a brain block on a microtome pedestal. Use a monofilament to cut to avoid tissue sticking to the knife and distorting.