Abstract: A plate for positioning a radiation test wipe in alignment with a sensor on a radiation monitoring instrument includes a recessed mounting area on the plate that conforms to the geometry of the wipe. Guide members on the plate slidably engage brackets attached to a back panel of the instrument. The plate is therefore removable and can slide into a position along the instrument where it contacts a slide stop integral to the brackets. This causes the test wipe to be aligned directly under the sensor to provide consistent readings.