The sections of trunk are usually beech without visible knots from the forests of Navarre. For competitions, the trunk sections closest to the roots or branches are used as they are of less value to the wood industry. The trunks are categorised according to their circumference using an old Basque measure called ontza, equivalent to 0.0254m. They commonly are used in the following sizes:
| Ontza | Basque name | translation |
| 36 | oinbetekoa | one of a full foot |
| 45 | ||
| 54 | kanaerdikoa | one of half a kana |
| 60 | ||
| 72 | oinbikoa | one of two feet |
| 80 | ||
| 108 | kanakoa | one of one kana |
| 110 | ||
The axes are between 2.4 and 2.8kg heavy with a rounded blade and each aizkolari uses a number of them in a competition. The logs are between 0.5-0.8m long for competitions where one aizkolari stands on the log and between 0.8-1.2m long for competitions where two stand on it.
They can be held with each aizkolari having two helpers. The botilero (botillero in Spanish) holds the towel and brings new axes. The prestatzaile (enseñador in Spanish) checks the two halves are fully separated (they sometimes appear to have but are still connected), dictates the rhythm and indicates where best to hit next.
In a famous competition held in 1983 in Tolosa, two aizkolaris called Jose Mari Mendizabal and Mikel Mindegi had a wager to chop six 110 ontza trunks and 52 kanaerdikoa (a total of 100 kanaerdi) each in less than 5 hours. Mendizabal won the competition and 2 million Pesetas taking just 4:12hrs, Mindegi 4:29hrs. But the most famous aizkolari was probably a man nicknamed Santa Ageda who competed in an epic event in the bullring of Azpeitia in 1903.
Many aizkolariak compete into high age. In 1900, Augustin Unanue who was aged 75 at the time, famously chopped a log of 1m diameter in 4 hours. Famous competitions often lead to the composition of bertsos in honour of the event.
The most important modern day competition is probably the Urrezko Aizkora, the "golden axe" competition where the best aizkolaris from all over the Basque Country compete against each other individually or in pairs. There are several categories, including two junior competitions for people under the age of 23 and 18. The competitions are held in different places in the Basque Country over a period of twoo months to establish a winner. Held since 1997, it has been held annually since. Other important competitions are the Donostiako Urrezko Kopako ("gold cup of San Sebastián"), the Euskal Herriko Lehen Maila ("premier league of the Basque Country") and the provincial competitions.
| Year | Singles | Pairs |
| 1997 | ||
| 1998 | Joxemiel Peñagarikano | |
| 1999 | ||
| 2000 | ||
| 2001 | ||
| 2002 | ||
| 2003 | ||
| 2004 | Floren Nazabal | |
| 2005 | Donato Larretxea v Floren Nazabal | |
| 2006 | Floren Nazabal v Jose Mari Olasagasti | |
| 2007 | Floren Nazabal v Jose Mari Olasagasti | Floren Nazabal & Juan Jose Azpilikueta v Donato Larretxea & Jose Juan Barberena |
| 2008 | Floren Nazabal v Donato Larretxea | Donato Larretxea & Aitzol Atutxa v Anjel Arrospide & Aierbe II |
| Year | Winner | Runner-up |
| 1989 | ||
| 1990 | ||
| 1991 | ||
| 1992 | ||
| 1993 | ||
| 1994 | ||
| 1995 | ||
| 1996 | Jose Mari Olasagasti | |
| 1997 | Donato Larretxea | |
| 1998 | Jose Mari Olasagasti | |
| 1999 | Jose Mari Olasagasti | |
| 2000 | Joxemiel Peñagarikano | |
| 2001 | Jose Mari Olasagasti | |
| 2002 | ||
| 2003 | Donato Larretxea | |
| 2004 | ||
| 2005 | Mikel Mujika | |
| 2006 | ||
| 2007 | ||
| 2008 | ||
| Year | Winner | Runner-up |
| 1997 | Joxemiel Peñagarikano | |
| 1998 | ||
| 1999 | ||
| 2000 | ||
| 2001 | ||
| 2002 | ||
| 2003 | Iñaki Azurmendi | |
| 2004 | ||
| 2005 | ||
| 2006 | ||
| 2007 | ||
| 2008 | Iñaki Azurmendi | Joxemari Olasagasti |
| Year | Winner | Runner-up |
| 1989 | Donato Larretxea (35:09) | |
| 1990 | Joxemari Olasagasti (31:41) | |
| 1991 | Anjel Arrospide (28:20) | |
| 1992 | Anjel Arrospide (27:39) | |
| 1993 | Anjel Arrospide (27:53) | |
| 1994 | Anjel Arrospide (28:34) | |
| 1995 | Donato Larretxea (27:17) | |
| 1996 | Anjel Arrospide (29:11) | |
| 1997 | Donato Larretxea (29:22) | |
| 1998 | Antonio Senosiain (30:00) | |
| 1999 | Joxemari Olasagasti (27:39) | Joxemiel Peñagarikano (30:08) |
| 2000 | Joxemiel Peñagarikano (29:04) | Floren Nazabal (30:53) |
| 2001 | Joxemiel Peñagarikano (27:34) | Donato Larretxea (27:56) |
| 2002 | Donato Larretxea (29:03) | Joxemiel Peñagarikano (31:10) |
| 2003 | Joxemiel Peñagarikano (37:01) | Floren Nazabal (37:23) |
| 2004 | Floren Nazabal (35:28) | Joxemiel Peñagarikano (36:12) |
| 2005 | Floren Nazabal (38:52) | Joxemari Olasagasti (41:48) |
| 2006 | Floren Nazabal (31:47) | Joxemari Olasagasti (36:16) |
| 2007 | Joxemari Olasagasti (31:34) | Luis Txapartegi (32:57) |
| 2008 | ||
There is another variation combining the chopping competition with a race.
The use of large quantities of charcoal as fuel for the many foundries in the Basque Country in the 18th century together with the use of wood for shipbuilding led to large areas of woodland being cut down. In time, those country towns and valleys that were famed for their top wood-cutters turned out to be those that have safeguarded the wealth of their forests.
As popular competitions they were not recorded until the 19th century. Interestingly, the names of the competitors were not recorded but referred to by their place of origin or group, for example "one of Beizama", "the son of the house of Gorrizu", "the group from Nuarbe" or "the one from Beunza farm". To outsiders, the early competitions where known as fiestas Euskaras "Basque fiestas".