What is a Last?
A climbing shoe last is the beginning building block for a shoe. From start to finish, the last remains underneath all the materials that build up a climbing shoe. The last for a climbing shoe is essentially a plastic dummy foot with a beak tip instead of individual toes. Every shoe size has a last that determines the size and shape of the foot bed, toe box, and heel cup.
Types of Climbing Shoe Lasts
Slip lasts and board lasts are the two styles of building a climbing shoe. Although shoe-makers refer to them as different “lasts”, they actually build board and slip lasts around the same dummy foot. The processes and materials used in the making of the climbing shoe determine the last type.
Slip Lasted Shoes
A slip lasted shoe has an upper that wraps around your foot like a sock. It is separated by a midsole that sits between it and the outsole rubber. The finished product places the foot directly on the upper, which sits below it a midsole, and the rubber outsole.
Since there is less material between your foot and the rock. Slip lasted shoes tend to favor styles of climbing where the climber relies on shoe sensitivity and flexibility, like bouldering and/or overhanging climbing.
Board Lasted Shoes
Climbing shoes made with a board last are built around a stiff insole. The upper does not create a closed loop like on a slip last, it attaches underneath the midsole.
A board last is more like a traditional tennis shoe for when you are using them you are stepping directly on an insole. So to recap, with a board lasted climbing shoe you have an insole, a midsole, a little bit of the upper, and then the outsole rubber between your foot and the rock surface.
Slip Last Vs. Board Last
The popularity of overhanging climbing has enforced slip lasted shoes as the primary climbing shoe last. The increased sensitivity of a slip last performs exceptionally well for precise footwork because you can better feel the rock surface. Also, the increased flexibility makes them good for smearing but not great for edging.
Long multi-pitch routes where you are climbing all day would benefit from the support of a rigid insole that comes from a board lasted shoe. Since board lasted shoes are stiffer they compromise their smearing ability for exceptional edging.
A plus about board lasts is that they are more durable than slip lasted shoes so they are known to be able to stand multiple resoles. The stiff insole on a board last shoe best preserves the original shoe shape making them stretch less than their slip lasted counterparts.
The next option for climbing shoe lasts are their shape, this decides how aggressive the fit will be. The picture above shows the two ends of the spectrum between neutral and aggressive. The neutral shoe has a flat last and moderate to aggressive shoes has a downturned or cambered last.
The most comfortable fitting shoe will have a flat last because it will not try and alter the shape of your foot. They are recommended for beginning climbers, crack climbing, and are prefect for keeping on all day.
Climbing shoes that have a downturned last will arch more to point your toes down. This type of last offers more power to the toe because your foot is in a position where all the weight of your foot rests on the tip of the shoe. As shoes become more downturned, they tend to be less comfortable because this defies the way weight dissipates throughout your whole foot in a regular shoe.
A shoe that is asymmetric will concentrate power to the inside edge of the shoe, primarily to the big toe. Asymmetry is most common in aggressive shoes that require precise footwork, because they put all the power at one single point.
To recognize asymmetric shoes you can look at the bottom of a shoe and notice how the toe point deviates from the heel.
A climbing shoe can have a straight or a downturned last, and also be asymmetric. Shoe that are asymmetric tend to favor feet with higher arches because they are better cambered to accommodate such a contorted position.