Retractable targets of carbon fibres with nominal diameters of 30, 7 and 4.5 μm have been in use at the collision point of the SLC (the SLAC Linear Collider). The target mechanism is compatible with the Mark II detector now in place at the collision point. Beam profiles are measured in horizontal and vertical axes by using magnetic dipoles to scan the beams across the fibres. Two signal detection mechanisms are available. Electron emission from the fibres is measured with the help of charge-sensitive amplifiers. Bremsstrahlung from the fibres is detected by downstream counters. Examples of measurements are given, and limits on the use of the techniques are discussed.