A handheld apparatus (2) for checking the tension of the wire (15) includes a support (3) with two spaced pegs (5,6) mounted on it. A spring (7) mounted on the support (3) between the two pegs. A strain gauge (14) is mounted on the spring and measures the displacement of the spring (7). A fully portable power supply is connected to a computer (9) with a readout (8). In use, the wire (15) is arranged in a predetermined path over and/or under the pegs (5,6) so that it presses against the spring (7). The amount the spring (7) is displaced, which is related to the tension, is measured by the signal from the strain gauge. The signal is passed to the computer (9), which calculates the tension from this measurement and displays the result on the readout (8).