If you have an irregular opening to fill, it is best to take a tracing of the opening. Usually this will be in larger openings and a helper may be necessary to assist.
Materials
The material used to take the template must have a few characteristics:
It must be stiff enough to have the minimum possible bend over the width or height of the opening
It must be easy to mark with a pencil or other implement
It must be easy to cut or shape
It should be light to make it easy to lift it to the opening for the many adjustments that will be required.
A number of materials can be used: stiff card, mounting board, corrugated cardboard, thin plywood, and many other sheet materials. I have found double walled stiff corrugated cardboard easy to use.
Irregular rectangles
If you have found or can see that the opening is not a true rectangle and cannot determine where any right angles are, you need to take a template.
The objective is to make a piece that will fit into the opening without bending or being too small for the space. It will be the same size as the finished panel and so you will be able to put the finished panel into the opening without needing to trim or expand the panel.
First, trim the sheet of material you have chosen to use to a size a little larger than the measured size. Place the uncut side along one of the long sides of the opening. If the opening is a portrait format, place it on the right or left side as convenient to you.
Next, adjust the bottom by marking a line on the sheet. This is where a second person is very useful. One person can hold the sheet in place on outside of the opening and the other do the marking from the inside –in the case of the rebate being on the outside and vice versa if the rebate is on the inside. The marked line should be as close to the edge of the rebate as possible. The special case of an opening in stone will be dealt with separately.
Then take the sheet to a place where it can be safely cut. A long metal straight edge and craft or “Stanley” knife are often the best aids to cutting straight lines. Replace the sheet into the opening after cutting, and make any adjustments to the size and angles of the sheet at the bottom by marking and cutting as necessary.
When the side and bottom are adjusted, start on the other side. Proceed as for the bottom. When the side is finished, start on the top. Finally, present the whole sheet to the opening to make sure it slips into place with no snags, or bending of the sheet.
It may be that the opening is too large for a single sheet. In that case you will need to work with two or more sheets and try them together for the final fitting into the opening. You can put them together in the window. You can fasten them together with tape or other fasteners to make one sheet. You can also make two parallel lines both at angles and at intervals across the sheet so that when you get back to the studio you can exactly reproduce the full sheet by matching the marks and then firmly fastening them together. This makes transport of large templates much easier.
You will know that a panel made to a template made in this way will fit into the opening, no matter how irregular the opening may be.
Circles
Occasionally the window is circular and sometimes an oval. In both cases a template is important. The circles and ovals are rarely is exact or symmetrical. Take the template in the normal way and then ensure you mark the verticals and horizontals for the opening. You often can use the jointing in the woodwork to help with these. Also mark any other reference points from the opening. Finally, mark which is the outside and which the inside.
Round heads
Round headed openings can be considered as a special case of a circle. The horizontal you must find is the shoulder of the window. This is the place from which the curve springs on each side. The opening is generally vertical up to this point and then begins the curve.
You need to make sure you have marked where this shoulder is on the template. You should indicate any reference points from the frame onto the template.
The join to the lower part of the window must be made obvious. Normally there will be an overlap between the lower rectangular template and this approximate half circle. You need to mark where this overlap occurs, if you do not fasten the two sheets together. This can be done by marking across the two sheets in a few places. This will enable you to join them exactly back at the studio.
Irregular openings
Irregular openings such as trefoils and other tracery need to have templates taken with consideration on how the final panel can be put into the opening. In the cases where the whole of the rebate is exposed, it is normally possible to put the panel in as a single whole piece.
So, the template is taken as for any other opening. It is more complex and time consuming as there are so many more sides than in a simple rectangular or circular opening.
Stone
When the opening is in stone, slight variations occur in the process of taking a template. The main difference is that the rebates are concealed. The rebates are slots into the stone. Thus, the template must slip into the slotted rebate. In these cases, the stiffer the material being used to take template, the better. Usually, thin plywood is the best material, as it has to be manipulated many times and in ways similar to the final panel.
Things are further complicated, as tracery is more common in stone than in timber framed openings. A complex opening shape may require two or more parts to enable the panel to be inserted. The taking of a template will help greatly in figuring out how the panel will be inserted into the opening.
Additionally, when the template is in position, you should mark the visible portion of the opening onto the template. Mark which is the inside and which the outside. Finally, mark on each template which side has the deeper slot as this will help in installation.
Using these methods of taking templates will make restoration or drawing up a new design much easier and more accurate, leading to an easier installation.
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