How might I make a template to fit the top of my desk?

Question

My desk is nearly finished; all that's left is to have the glass top cut. To do this, I need a template to give the glass shop. I can't just give them dimensions since it's not perfectly square. More importantly there are pegs on the frame. The glass is to be "keyed" so that the pegs will keep it from sliding, and I need to ensure that the glass aligns near perfectly with them (perhaps 1mm of play on either side of the pegs).

An image of the desk is below. note that the center of the desk is set roughly half an inch below the borders, so simply laying paper down and marking it is somewhat troublesome.

How might I go about creating the template?

Answer 1

Geometric solution

Using a large compass or trammel, you can precisely gauge all the distances and transfer them to a large template of whatever material you choose (paper, cardboard, hardboard, plywood, etc.). For each point you need to lay out, you just need at least two reference points and the distance from each reference point to the point you're trying to transfer.

1. Place the (center) point of the compass on a reference point on your table and adjust the radius to match the distance to the point you're transferring.
2. Lock in the setting, then move the compass to the corresponding reference point on your large sheet of paper and strike an arc.
3. Repeat for the second (and optionally third) reference point. The point you're transferring will be at the intersection of the two (or more) arcs.

Repeat the above steps for as many points as you need to transfer.

Note that if you gauge and mark from 3 or more reference points, any error will be apparent because not all the arcs used to transfer that point will intersect at a single point.

There are also various other geometric construction techniques you can use to construct regular or irregular shapes using just a compass and/or straightedge.

Direct solution

Originally I was thinking you needed to cut square holes in the glass, but after rereading your question it sounds like you just want to notch out the corners of a rectangular sheet of glass. That makes creating a template much easier:

1. Cut a piece of cardboard, hardboard, or thin plywood several inches wider than the half the distance between the left and right pairs of pegs.
2. Using a knife and metal rule or straightedge, mark the positions of the pegs.
3. Cut out notches for the pegs.
4. Repeat for the other side.
5. Securely glue or tape the two slightly overlapping sides together.
6. With the template still in place, use a knife and metal straightedge to trim (or mark, if using thicker material) the template to match the outside perimeter (the perhaps slightly out-of-square rectangle that encloses the pegs).
7. If the material was too thick to trim with just the knife, remove the template and use a track saw (or a circular saw with a straightedge guide) to finish trimming the template along the knife marks.

Answer 2

Simplest answer may be a large sheet of paper (or several firmly secured to each other), fitted precisely to the space. If assembling, use two overlapping pieces, cut away if necessary, to fit the corners. Make sure it's all well secured so nothing can slide out of position, trap it between two large sheets of cardboard for safe travel, and...

Or just get precise measurements of all sides and both diagonals? Should be possible to get the angles from that.

You may need to allow for wood movement, if this glass is going to be inset.

Strong suggestion: Find a glass shop that has worked with furniture makers before and ask how they'd do it.

Answer 3

A variation on the answers above is to make a template like cabinet makers do for counter tops. They will use either strips of 1/4 sheathing/plywood, place them at the perimiter and glue the parts together to make a template. As an alternative , you could get large sheets of poster board, place them to the edges and glue or package tape them together. You can locate your holes by cutting an oversize hole at each location and then apply strips of cardboard to exactly define your holes.