Canvas tacks are used to pin down the canvas on a stretcher frame.

A stretched canvas covers the sides of the frame and tacks are driven in evenly along the edges to fix the canvas with equal tension to the frame. By removing the tacks, a canvas can be restretched as many times as you wish. Ordinary woodworking nails (commercially-sold tacks are similar to these in shape) have a cylindrical shape with a sharp tip and are difficult to remove. Canvas tacks, on the other hand, resemble a wedge-shaped pyramid from the head down and are only around 13 mm long. Therefore, they are relatively easy to pull out and the canvas can be removed without damage (long tacks which do not come off easily are also available). Pincers and flathead screwdrivers can be used to remove the tacks.

Canvas tacks are usually made of iron or stainless steel. Iron tacks are cheap, while stainless steel tacks are resistant to rust. It is better to use rust-resistant tacks because tacks that have rusted due to moisture can cause damage to the canvas and the stretcher frame, or become impossible to remove when restretching the canvas. More recently, there are brass-plated iron tacks, which are cheaper and less prone to rusting, as well as Eco-tacks, which are made of resin and do not rust and are also environmentally-friendly because they return to the soil.

As an alternative, staple guns are also sometimes used. These are basically construction-use staplers which use straight-legged staples to affix the canvas to the frame. However, this is nothing more than a substitute and the staples’ strength and durability during long-term storage will be a concern. These staple guns take both cheap steel staples and rust-resistant stainless steel staples which are 12 mm wide and either 6 mm, 10 mm or 13 mm long (13 mm only for stainless steel). Using longer staples ensures that the canvas is firmly secured.

Be careful when using canvas tacks because the pointed tip can be dangerous. Take sufficient care when using and storing them. Iron tacks are best stored in dry places as they rust easily. Canvas tacks can be purchased at ordinary art supply stores.