When should callipers not be used for measuring shot in lawn bowls?

Callipers should not be used for measuring when assessing the distance between a jack in the ditch and a bowl on the green. This is because callipers are designed for measuring distances between two objects that are relatively close together, enabling the precise determination of which is closest to the jack or the designated target.

When a jack is in the ditch, it may not be readily accessible or visible in comparison to a bowl, making it challenging to measure the distance accurately using callipers. Instead, a tape measure is more appropriate for discerning the distances in this context, particularly since the jack being in the ditch could complicate the measurement path.

In other scenarios, such as measuring the distance from the mat to the jack or when the bowls are in closer proximity, callipers could be effectively used. Additionally, weather conditions like rain do not directly affect the use of callipers but may impact visibility or the playing surface, making it more critical to use the appropriate measuring tool for clear and accurate results.