A strainer bar is used to construct a wooden stretcher frame

Picture frame

A picture frame is a decorative edging for a picture, such as a painting or photograph, intended to enhance it, make it easier to display, or protect it.-Construction:...

 used by artist

Artist

An artist is a person engaged in one or more of any of a broad spectrum of activities related to creating art, practicing the arts and/or demonstrating an art. The common usage in both everyday speech and academic discourse is a practitioner in the visual arts only...

s to mount their canvas

Canvas

Canvas is an extremely heavy-duty plain-woven fabric used for making sails, tents, marquees, backpacks, and other items for which sturdiness is required. It is also popularly used by artists as a painting surface, typically stretched across a wooden frame...

es. They are traditionally a wooden framework support on which an artist fastens a piece of canvas. They are also used for small-scale embroidery

Embroidery

Embroidery is the art or handicraft of decorating fabric or other materials with needle and thread or yarn. Embroidery may also incorporate other materials such as metal strips, pearls, beads, quills, and sequins....

 to provide steady tension, affixing the edges of the fabric with push-pins or a staple gun before beginning to sew, and then removing it from the frame when the work is complete. Strainer bar frames are usually in the shape of a rectangle

Rectangle

In Euclidean plane geometry, a rectangle is any quadrilateral with four right angles. The term "oblong" is occasionally used to refer to a non-square rectangle...

, although shaped canvas

Shaped canvas

Shaped canvases are paintings that depart from the normal flat, rectangular configuration. Canvases may be shaped by altering their outline, while retaining their flatness. An ancient, traditional example is the tondo, a painting on a round canvas: Raphael, as well as some other Renaissance...

es are also possible.

A stretcher frame constructed from strainer bars should not be confused with one constructed from stretcher bar

Stretcher bar

A stretcher bar is used to construct a wooden stretcher frame used by artists to mount their canvases. They are traditionally a wooden framework support on which an artist fastens a piece of canvas...

s. Strainer bars are fixed to one another with wood glue

Wood glue

Wood glue is an adhesive used to tightly bond pieces of wood together. Many substances have been used as glues.-Types of wood glue:* For many centuries animal glue, especially hide glue was the traditional glue for all kinds of woodwork. It is still used today, mainly for musical instruments and...

, nails

Nail (engineering)

In woodworking and construction, a nail is a pin-shaped, sharp object of hard metal or alloy used as a fastener. Formerly wrought iron, today's nails are typically made of steel, often dipped or coated to prevent corrosion in harsh conditions or improve adhesion...

 or staples

Staple (fastener)

A staple is a type of two-pronged fastener, usually metal, used for joining or binding materials together. Large staples might be used with a hammer or staple gun for masonry, roofing, corrugated boxes and other heavy-duty uses...

, often in conjunction. Strainer bar frames are often reinforced with other fixed elements such as corner and cross braces. These frames are not built to accommodate the insertion of tightening key

Tightening key

Corner Key is a small wedge or block inserted into the slotted inside corners of a canvas stretcher frame.The key is tapped in to expand the stretcher bars slightly, tensioning the canvas...

s into their corners to further tighten the canvas stretched upon them as a stretcher bar frame would.