What must a marker do if they are asked to show the position of the jack?

When a marker is asked to show the position of the jack, their responsibility is to indicate the jack's location without physically interfering with it. This is important for maintaining the integrity of the game and ensuring that players can accurately assess the situation without any alteration. By pointing out the position, the marker provides clear guidance without altering the play or the existing arrangement of the bowls.

Signaling with hands could cause confusion or misinterpretation since it might not provide a precise indication of the jack's exact position. Physically moving the jack not only disrupts the game but also could change the dynamics of how the subsequent shots are played, which is not allowed. Measuring the distance is unnecessary as the focus is on visually showing where the jack lies rather than obtaining quantitative data about its position. Thus, the correct approach by the marker is simply to point out where the jack is located.