Girth (tack) slightly too small, a girth extender may be used. A girth extender attaches to the billets of the saddle and lengthens them, so that a shorter girth may be used. Most jumping saddles have three billets. This not only allows the rider a spare should one break, but can also provide an adjustment option. For horses on which the saddle sits nicely, neither slipping forward or back, the first and third billets should be used. On horses where the saddle slips back, the first and second billets should be used. The second and third should never be used together, as
Matroid girth oracle, it is impossible to find the girth using a subexponential number of matroid queries. Similarly, for a real linear matroid of rank , with elements, described by an oracle that gives the orientation of any -tuple of elements, it requires formula_1 oracle queries to determine the girth. Computations using a girth oracle (an oracle that reports the smallest dependent subset of a given set of elements) have also been considered. Matroid girth In matroid theory, a mathematical discipline, the girth of a matroid is the size of its smallest circuit or dependent set. The cogirth of a matroid is