Bawm build with bamboo and thatch in their mountainous forests. They made the apostles and prophets become the roof ridge pole and Jesus the central uprights which support it. I asked why not the corner uprights since Greek has a term that is translated in English as ‘cornerstone.’ Bawm translators responded that the central uprights are more important than the corner ones, and Greek refers to the most important stone. (“Corner uprights” used in 1 Timothy 3:15.) (Source: David Clark)

Similarly, Chris Pluger tells the following from the translation into Tsamakko: “At the end of Ephesians 2, Paul uses the idea of a building to show that people of all nations and backgrounds are united together by faith in Christ. This building is pictured as standing on a stone foundation, and believers are ‘joined together’ as parts of that building. Christ himself is the cornerstone on which everything is based. However, the Tsamakko people of southwest Ethiopia do not build on stone foundations, and their buildings are traditionally round. This makes the idea of a ‘cornerstone’ difficult for several obvious reasons. In the Tsamakko translation of Ephesians 2:20, Christ is the mososso — the big center pole of a house that holds up the roof and the entire structure of the building. The apostles and prophets are the other poles that support the frame of the house. And believers are the house itself — all the pieces that make up the walls and the roof. We are all joined together as one, and Christ is the thing that keeps us together!” (for a complete back-translation of that verse in Tsamakko, see complete verse (Ephesians 2:20).

In Mono, translators used “main post,” in Martu Wangka “two forked sticks with another long strong stick laid across” (see also 1 Peter 2:6-7.), and in Arrernte, the translation in 1 Peter 2:7 (in English translation: “the stone . . . became the very cornerstone”) was rendered as “the foundation… continues to be the right foundation,” (source for this and two above: Carl Gross) and in Uripiv and Sabaot it is the “post” (source: Ross McKerras and Jim Leonhard in Holzhausen / Riderer 2010, p. 50). Likewise, in Hakha Chin it is the “central upright poles of a house.” (Hakha Chin speakers are mountain people who build houses with bamboo and palm thatch, not stone) (source: David Clark)

In Ixcatlán Mazatec it is translated with a term denoting the “the principal part of the ‘house’ (or work)” (source: Robert Bascom), in Enlhet as “like the house-root” (source: Jacob Loewen in The Bible Translator 1969, p. 24ff. ), in Q’anjob’al it is translated with with the existing idiom “ear of the house.” (Source: Newberry and Kittie Cox in The Bible Translator 1950, p. 91ff. ), in Desano as “main support of the house,” and in Tataltepec Chatino as “the best stone” (source for this and one above: Viola Waterhouse in Notes on Translation August 1966, p. 86ff.).

Shuar translates as “that stone was placed to the main house pole.” The Shuar use stones in house building either at the bottom of the posthole as a base for the house pole to rest on, or as chocking material around the post to hold it firm. Either function is acceptable here particularly as applied to the main house-pole. In Ocotlán Zapotec it is “master stone of the house.” This is a special stone they put into the foundation as sort of a guide stone of how the foundation is to true up. (Source: B. Moore / G. Turner in Notes on Translation 1967, p. 1ff.)

In Matumbi it is “the great foundation stone.” It’s the first large stone you place for a house, the one that determines where all the other stones will go, but unlike in Greek thought it’s often in the center of a building instead of a corner. (Source: Pioneer Bible Translators, project-specific notes in Paratext)

See also rock / stone, foundation on rock, and foundation.