When folded, the tool 50 of the invention comprises three members 7,8 and 9 stacked together with the thin edges 21,22 and 23 of the rectangular profiles aligned. In the folded position, the tool 50 will be held closed by means of tension generated by the locking mechanism 4 which includes pin 11 and spring 16 with the spring loaded push button head 13 and the enlarged washer 15 affixed to the other end of the pin or rivet 11. The tool 50 is thus kept in this position and prevented from falling open on its own. Approximately six pounds of pressure is required to disengage the lock and compress the spring 16. The intermediate pin portion 11 of the locking mechanism 4 engages the notch 30 in the leg 9 to limit the movement of leg 7 during folding.

In the open position shown in FIG. 2, the tool 50 will form a right angle at the intersection of two of the members legs 7 and 8, and the other two ends will be joined by a diagonal leg 9. In

the preferred embodiment, the dimensions of the legs will be three feet-leg 7, four feet-leg 8 and five feet-leg 9.

The tool 50 creates and guarantees a perfect right angle by design, employing the mathematic ratio of a 3-4-5 triangle. By design, the tool 50 will retain its accuracy due to the fact that each of the three members 7,8 and 9 are continuously attached to one another. This maintains the integrity of the tool 50. Two of the attachment points are precisely located rivet pivot points 10a and lOb. The third point is a pin or rivet 11 with a push button head 13 at one end and an enlarged washer 15 affixed to the other end engaging the surface of leg 7 which rides in a skewed slot 12.

The pin 11, as thus described functions as a spring loaded positive position lock 4 keeping the tool 50 in the open position. Pressure on the push button 13 releases the spring lock 4 enabling the tool 50 to close to its folded or closed position shown in FIG. 1.

Friction/tension is maintained constantly by spring 16 to provide a controlled motion of the members 7,8 and 9 to prevent them from free falling.

The pin 11 which rides in the slot 12 is a two piece internal rivet with a push button head 13 at one end and a washer 15 affixed to the other end. The washer 15 has downwardly extending walls 26 with a central recess 27 within which the cylindrical walls 28 of the push-button rivet 29 are mounted. The washer head 16 includes an enlarged circular top 40 joined to an intermediate portion 31 of lesser diameter which engages the semi-circular aperture 50.

The member 7 includes a notch 16 which the pin 11 engages prevent- ing the tool 50 from over closing or opening in the wrong direc-

tion. The slot 12 in the member 7 is skewed at an angle relative to the edges of the member 7. At the end of the slot 12, the spring 16 pulls the post or pin 11 into a semicircular hole thereby creating a positive lock such as shown in FIG. 3b. The pin 11 is shown in an open position in FIG. 3a.

As a further advantage, the hole 5 maintains the tool 50 in a proper locked position even if the forward portion of the hole 5 becomes distorted due to repeated usage.

In the preferred embodiment the members 7,8 and 9 are of elongated rectangular bar stock approximately 1/8 inch thick by 2 inches wide. As mentioned often the legs 7,8 and 9 are 3,4, and 5 feet long respectively which creates a right angle in the open position in order to layout perpendicular lines.

It is within the scope of the invention to make an assortment of sizes and models of this tool 50, all of which retain the ratio of 3-4-5 triangle. It is also possible to use the teachings of this invention with an isosceles triangle which has two 45o angles and a 90o angle.

While the invention has been explained by a detailed descrip- tion of certain specific embodiments, it is understood that various modifications and substitutions can be made in any of them within the scope of the appended claims which are intended also to include equivalents of such embodiments.

BACKGROUND OF THE INVENTION The proposed invention referred to herein as A SQUARE, was conceived during many years of applying the theory of a 3-4-5 triangle during the practice of laying out perpendicular lines in the construction industry. Creating a perpendicular line, which is any substantial length (approximately 4'or greater) requires greater accuracy than a framing square can provide due to its size.

It is this need for accuracy that dictates the use of a 3-4-5 triangle using the present invention.

Typical application of the 3-4-5 triangle, prior to this invention, comprised using two tape measures simultaneously, which required two people to perform the operation with any efficiency.

A SQUAREM is a tool which creates 3-4-5 rigid triangle. Advanta- geously, the tool folds to a compact state with the sides of the triangle aligned to allow it to be portable and storable. The invention has a wide range of uses in the construction industry for many types of lay out, i. e., framing lay out, masonry lay out, concrete form work, finish carpentry, cabinet installation, construction supervision, ceramic tile layout, VCT tile lay out, <BR> <BR> <BR> etc. Furthermore, the design of A SQUAREE gives it the ability to function as a proficient sheet rock square by resting the three foot leg on the ground rather than the traditional sheet rock square which hangs from the board. The invention may also be produced in a variety of sizes and configurations for example, an isosceles triangle.

Among the prior art patents of general interest are U. S. patents 124,22; 778, 659; 1,394,088; 2,667,697; 3,345,750 and 4,955,141. The prior art patents are not directly in point and fail to provide an anticipation of the features which have made this invention a great success.

SUMMARY OF THE INVENTION This invention relates to layout tools and particularly to tools providing a right angle for laying out perpendicular lines of any substantial length. The invention comprises three legs or members, all of which are permanently attached at pivot points.

Two of the three points are precisely located pivot points. The third point is a precisely located resilient locking stud or rivet which slides in a skewed slot and permits the adjoining two members to slide into a parallel plane to one another in a compact folded position when not in use and then into a locked open position creating a perfect 3-4-5 triangle for layout purposes when in use.

Critical to the design is the fact that the manner in which the members are connected and aligned guarantees a perfect and not distorted 3-4-5 triangle. This is crucial to maintain the accuracy of the tool.

Accordingly, an object of this invention is to provide a new and improved layout tool which provides a right angle.

Another object of this invention is to provide a new and improved layout tool which includes a 3-4-5 triangle to provide an accurate 90o angle for layout purposes.

A further object of this invention is to provide a new and improved layout tool involving a relatively large 3-4-5 triangle which readily slides into a compact form with the legs of the triangle in a substantially parallel plane.

A more specific object of this invention is to provide a triangular right angle layout tool for laying out perpendicular lines wherein the legs are pivotally mounted to one another at thei-ends and one end includes a spring-loaded rivet which slides in a skewed slot in an adjacent leg to collapse the triangle into linearly parallel legs.

BRIEF DESCRIPTION OF THE DRAWINGS The above and other objects and advantages of this invention may be more clearly seen when viewed in conjunction with the accompanying drawings wherein: FIG. 1 is an elevation side-view with the invention in a closed position depicting the stacking arrangement of the members or triangle legs and the pivot point mount- ings; FIG. 2 is a top plan view of the invention in an unlocked position depicting the overall footprint of the layout tool in an unfolded triangular arrangement; FIG. 3a is an enlarged cross-sectional view of the rivet locking mechanism in an open position and FIG. 3b shows the rivet mechanism in a locked position; and, FIG. 4a shows the washer portion of the rivet and FIG. 4b shows the internal portion of the rivet with the push button head.