So what are they and how do they help installers? Trammel points are two sliding points with a beam. The beam is generally a straight section of wood cut to fit the trammel points (Photo 1). The length of the beam can vary depending on the size of the area being laid out. Trammels are used to make reference marks for the layout of right angles, 45 degree angles, and ellipses. Laser squares are being used more and more but the costs are still relatively high for a quality laser. Trammels offer a more affordable solution with the same end results.
In order for us to use trammels a primary line must be established. For the primary line, try to start in the largest area of the installation and if possible, utilize an exterior wall as these are generally straighter than the interior walls. The primary line should run the longest length possible.
Let’s do a lay out of a jobsite. Take a measurement across the width of the room at each end (Photos 2, 3). In Photo 2, the measurement is 244.5 inches. In Photo 3, at the other end of the room, the measurement is 245 inches. Divide 244.5 inches in half and make a mark on the sub-floor, the mark should be 122 ¼ inches at that end of the room. At the other end of the room, divide 245 inches and make a mark on the sub-floor, this mark should be at 122 ½ inches. Even though there is a slight difference in the widths at each end, the primary line will be established in the center of the room. What we have done is made two reference marks at each end of the longest portion of the room. Strike a line between the two reference marks and this now becomes our primary line (Photo 4). The primary line will be the line in which all intersecting lines will be based from.
Take the length measurement along the primary line only. Now, this is where many installers make a mistake. I have had installers take a measurement on each side of the room in the length (the same way we measured across the room), and then strike an intersecting line to try and create a right angle. This will not work as the room may be out of square, as this one is. It is essential to square up to the primary line. Once squared up to the primary line, then we can determine how square the room is in relationship to our lines.
In Photo 2 there is a door opening. In order for us to have a wall to measure from, a line was chalked across the doorway to create a wall for the purposes of this portion of the article. From that chalk line to the other wall, a measurement was taken along the primary line only and measured 282 inches. Take the length measurement divide by 2 and place a mark on the primary line. This mark is the center of the room (Photo 5).
Adjusting the Trammel PointsThe trammel points can be adjusted to any distance apart from each other. The further out you can go the better. Our beam measured approximately six feet. The distance that the trammels are set at in the photo are approximately twenty inches, the beauty of the trammels is that you DO NOT have to use a tape measure to set the distance between the points.
Reference Marks for Secondary LineThe next step is to create the secondary line. This line will give you a true 90 degree angle. Starting from the CENTER POINT (A), strike an arc across the primary line (B) and another on the other side of the center point (C) Try to keep the center point trammel in position rather than removing and replacing it to create the arcs, this will maintain exactness (Photo 6).
The next step is to open up the distance between the trammel points, once again a tape measure is not necessary. We opened our trammels approximately three feet apart.
Using the marks just established on the primary line, place a trammel point on (B).
Strike an arc on each side of the primary line (D) (E), in line with the CENTER POINT. Repeat this process with the other mark that was established on the primary line (C) to (D) and (E) (Photo 7-8).
You should have two intersecting arcs on both sides of the primary line (D), (E). Strike a chalk line across the center of the intersecting arcs on both sides of the primary line; we have now established the secondary line which has created a true right angle (Photo 9-10). You can double check the squareness of the lines using the Pythagorean Theorem or more commonly known as 3-4-5 method.
Now we can determine how true or out of square the room actually is by taking measurements from the lines to the walls. There are times that you may have to make micro adjustments to the primary line depending on how far out of square the installation may be. Keep in mind that if you move the primary line any bit, you will have to reestablish the secondary lines as well. This would be more for aesthetics depending on the type of product you are installing.
We have now established the center point with a true right angle, so what does this mean now? If we are installing tile, the cuts at the walls will be balanced. At each end of the length the cuts will be equal, and at each end of the width the cuts will also be equal.
For hardwood floors, the cuts along the length next to the wall will be equal; the end cuts will not be as much of a factor. If you are installing borders and insets, balancing is very important aesthetically.
Carpet tiles, vinyl composition tiles (VCT), and other resilient tiles, will also balance out (Photo 11).
Layout of a 45-Degree AngleFor a 45 degree installation, follow all the steps that were covered for the primary and secondary lines. Once the primary and secondary lines have been established, you will need to readjust the trammel points back to the distance used for striking the two arcs on the primary line, refer to Photo 6. Once you have readjusted the trammels, strike an arc across the secondary line on both sides of the primary line (A) to (1), (A) to (3) (Photo 12). Place the trammel point on the arc that was made on the Primary line (B) and strike an arc straight out from the mark (2) (Photo 13). Next, place the trammel point on the arc that was made on the secondary line (1) and strike an arc at the intersecting point (2) (Photo 14).
Follow the same steps diagonally across from the marks that were just made (A) to (3), (3) to (4), (C) to (4) (Photo 15) Note: The visible intersecting arcs were to establish the secondary line and were highlighted with magic marker, the arcs for the 45 degree angle which we are using are not very visible in the photo that are marked on the secondary line.
Strike a chalk line at the intersecting arcs (2), (4), and (A). Now you have a perfect 45 degree angle (Photo 16). Not only will you have an exact 45 degree angle but you will also have balanced cuts at the walls by starting in the center of the room.
(Photo 17) Carpet tiles set at 45 degree installation
Multiple RoomsRemember the adjoining room where the large opening is, in Photo 2? How do you maintain the lines that were made in the large room and carry them through the rest of the installation? Follow the primary line in the large room and strike a chalk line through the next room. Now the next room has a primary line already established. The primary line may not be in the center of this room but remember, the primary line established in the large room and the center point are where all of the other lay out lines feed off of. You can still take measurements from this line to determine the squareness of each area. Adjoining the smaller room there is a corridor that leads into other areas. Since the primary line has already been established a reference mark can be placed on the primary line at any point. Since there is a corridor adjoining the smaller room, the reference mark on the primary line is placed so that the chalk line will fall approximately in the middle of the corridor (Photo 18). Follow the steps to establish the secondary line and strike a chalk line through the corridor. The secondary line from the smaller room has now become the primary line for the corridor. What starts out as a secondary line, ends up as the primary line into the next room or area.
Trammels can be purchased at many of the woodworking retails outlets around the country. For more information or assistance you can contact the International Certified Floor Covering Installers Association @ 816-231-4646.