. Attaching String-Lines
When running-in brickwork to a string-line, the line is attached at each end/corner, ensuring that it is aligned with the top edge/arris of the course to be run-in. There are two
basic methods of attaching string-lines: using a pair of metal pins, or using ‘L’-shaped corner blocks.
Fig. 134 Lines and pins in use.
When using metal pins, the ends of the pins need to be pushed into the joints of the brickwork, which causes damage to the joint that has to be made good later. Clumsy use of pins can also damage and disturb the brickwork itself. Pins have a further disadvantage in that it sometimes proves difficult to accurately align the line with the top arris of the bricks; this is made worse by their habit of working loose.
The second method uses ‘L’-shaped corner blocks (Fig 135), which can be created from off-cuts of timber or bought in pairs made of plastic. They are held in place by the tension of the line and have the distinct advantage of not damaging the mortar joints. However, they can only be used on external corners, which means that the use of pins is sometimes unavoidable. There must be enough tension in the line to ensure that the corner blocks stay attached and the line stays straight, but not excessively to the point that it disturbs the brickwork to which the blocks are attached. Most bricklayers avoid using pins unless they have to; the most common use of line pins is to have something to wrap the string-line around when it is not in use.
Attaching a string-line to a corner block is a four-step process (see Fig 136):
1. Pull the line straight through the front of the slot in the corner block and out through the back.
2. Bring the string-line back round the side of the block and pull it through the front of the slot again.
3. Pull the string-line tight and repeat this stage round the other side of the corner block.
4. Pull the string-line tight to complete the process.
Fig. 135 Lines and corner blocks in use.
The string-line is usually attached to the second corner block whilst the first block is held at the other end of the wall, kept in place by a dry brick or held by a colleague. This enables the bricklayer to gauge where to position the second block on the line, so that there is sufficient tension in the line for both line and corner blocks to be attached to the wall and be self-supporting.
It is sometimes difficult to ensure that the string-line is in perfect alignment with the arris of the course to be lined in. This is a common problem when using pins as they stick out and can be easily disturbed or, as is often the case, simply work loose. Accordingly, a bricklayer will often set the line slightly higher than necessary and then ‘sprag’ the line down to the top arris of the course to be run-in by using a dry brick. This ensures proper alignment of the string-line and also increases the
tension in the line slightly, making the line less likely to sag. Too much tension in the line can cause brickwork in the corner to be disturbed, particularly at the top of the corner where there are fewer bricks and less mass or ‘back weight’ to hold them in place.
Fig. 137 ‘Spragging’ the line down with a dry brick.