How do I centre the jack and check its length?

Law 42.2 requires the marker to check the mat is on the centre line, centre the jack, make sure it is at least 23 m from the mat line after centring, and place a jack that stops less than 2 m from the front ditch at 2 m (law 9.2). Bowls SA's domestic regulation on law 10.5 confirms the 23 m minimum.

Bowls SA's Markers Guide adds:

• Let the delivered jack stop, then centre it using your hands, without your shadow on it or blocking the number plate.
• Centre it before judging its distance; coloured pegs are only a rough guide.
• If you doubt it is 23 m, call the umpire to measure (after consulting the players, and always if either player asks).
• If the jack goes into or beyond the ditch, wholly outside a side boundary, or less than 23 m from the mat line, return it. The opponent may then re-lay the mat and deliver. If they also fail, centre the jack 2 m from the front ditch, and the player due to play first places the mat anywhere on the centre line at least 25 m from the front ditch.
• Nobody may challenge the jack's original position after the first bowl has been delivered.
• After the first end, the winner of the previous end chooses whether to place the mat, deliver the jack and play first, or let the opponent do so.