One of the joys of having young grandchildren is that you can again indulge in those pastimes that had to be abandoned as one's own children grew up. So you can decide for yourself whether the game described here is more for them or for me!

The arch is cut from a 14 1/4in (362mm) square of 3/4in (19.1mm) MDF. Now I was planning to make two versions of the game so I needed two arches both of which were cut from the one square; if, however, you only want to make one version, a semi-circular arch could be cut from a piece of MDF 14 1/4in (362 mm) x 8in (203mm) approx., just deep enough to allow for the beam trammel hole. This hole is drilled centrally in the square or central and 7 1/8 (181mm) from one long side of the rectangle and with a diameter which just accepts the pin of the beam trammel. A straight cutter is used in the router and the beam trammel is adjusted until the outer edge of the cutter is 6 7/8in (174.6mm) from the pin. The cutter diameter is not, therefore, significant. The block of MDF is fastened to a scrap board with double-sided adhesive tape, making sure that the tape holds both the centre disc and the outer part of the block. The cut is then made, gradually deepening the setting of the cutter until the block is cut right through. The arch is then completed by gently sawing the outer part of the MDF block into two or trimming to size if only one has been made.

Both ends of each side are mitred. A 45° bevel cutter is used in the router with the router in the table. Another simple jig, a rectangular piece of scrap MDF 1/2in (12.7mm) thick with a 45° bevel cut to a depth of 3/8in (9.5mm) across one end is used to guide the ends across the cutter. If no guide is used there is nothing for the side to bear on once the end has been reduced to a feather edge. The side and jig are held next to each other by hand pressure and the height of the cutter increased step by step until the bevel is complete. It will save a lot of cutter adjustment if both sides, the top and the bottom are all machined step by step at the same time. Both top edges of each side are rounded over using an 1/8in (3.2mm) radius rounding over cutter.

The 1in (25.4mm) long springs I finally used came from a Screwfix pack of compression springs but this would be a very expensive source if you didn't need a general supply. Maybe the 'bit-box' will provide what you need. The dimensions of the firing mechanism may have to be slightly modified to suit. I also thought that repeated use might well pull the corner woodwork apart despite the strength of modern glues, so, from the start I decided that the corner must be reinforced. It turned out that a Screwfix 50mm corner brace was ideal; if one of the holes nearer to the corner is carefully drilled out to 17/64in (6.7mm) (to allow free movement of the 1/4in (6.4mm) rod) then it came in just the right position. The corner brace was checked (and adjusted) for a true 90° angle and fixed in place with 3 M5 20mm pan head machine screws, washers and nuts. The height of the main hole was correct if the brace rested on the base. Appropriate holes must be drilled in the right hand side, in the bottom and in the short inner strip to match. The rod must be long enough so that when the assembly is pulled right back it does not come out of the hole in the short inner strip. A commercial wooden drawer knob was drilled out and stuck onto the outer end of the rod.

The firing mechanism underwent further development! Mark 1 used a washer on the rod, above the two springs, held in place by superglue, and omitted the loose washer between the springs. This was not successful as the washer eventually came loose and the springs twisted into each other. Mark 2 replaced the washer with an M6 nut drilled out to slide onto the rod and fixed in place with epoxy-resin adhesive. A loose washer was also added between the springs. This worked well but could not be removed if anything went wrong after assembly - without demolition that is! So in Mark 3 a small hole was drilled through the firing rod above the nut position and a small panel pin inserted and bent over. So far both Mark 2 (blue version) and Mark 3 (grey version) have been successful. A small piece of MDF is screwed to the right hand side to cover the spring mechanism.

The pattern of pinning is a matter of choice as you can see from the two examples I have made. It is simpler in the blue one and more complex in the grey with semi-circles in semi-circles and divided semi-circles but the same principles apply. Some bagatelle games have small cups, to accept but one ball, drilled out from the base but I did not incorporate this idea.

Finally a large number of balls are fired to see which cups are favoured and which are more difficult, so that a suitable numbering system could be devised. My wife then added these numbers with a marker pen. 10 steel balls (or more) 5/8in (15.9mm) in diameter are placed in the ball park. These balls, known as 'small steelies', come from a marble supply shop. The game is now ready for use.