You will be used to my love of words by now, but this lovely word came from Garry’s engineering background, referenced in today’s sermon on mutual affection. Tribology (a branch of mechanical engineering) is the science and engineering of interacting surfaces in relative motion. It includes the study and application of the principles of friction (the word itself is derived from the Greek word ‘tribo’, ‘I rub’), lubrication and wear, and the reason it came up in today’s sermon was as Garry discussed ‘bearing with one another’ (Eph 4:2).
Twenty-nine years ago Garry produced ‘a literary survey of rolling and journal bearings’ as his B.Sc. dissertation, a beautifully bound dissertation full of incomprehensible (to me) diagrams and equations that lives on our bookshelf gathering dust for the most part. 
Today it came back into its rightful glory, as Garry talked about how a study of bearings discovered that to make a totally smooth surface for bearings is not actually helpful, since bearings need some roughness to bed together properly.
[Still with me? I wasn’t! I was busy contemplating North-North-East and that kind of bearing, but apparently ‘a bearing is a machine element that constrains relative motion between moving parts to only the desired motion. The design of the bearing may, for example, provide for free linear movement of the moving part or for free rotation around a fixed axis; or, it may prevent a motion by controlling the vectors of normal forces that bear on the moving parts. Bearings are classified broadly according to the type of operation, the motions allowed, or to the directions of the loads (forces) applied to the parts.’ Now that we’ve got that clear, we can perhaps move on!]
Friction, it seems, is actually necessary for a bearing to mesh together properly. You might also expect similar materials to work well together in this engineering marvel, but apparently two different materials work better together, since it is good if one material has the capacity to absorb roughness. The spiritual application we can draw from this is quite clear. We are all different people, with different personalities. We often think church would be wonderful if everyone else were just like us, but that is not the case at all. God has designed us all differently for a purpose! Moreover, friction between people is inevitable at times and we have to learn to bear with each other. We literally have to learn to ‘grin and bear it’, absorbing the hurt from our brothers and sisters at times, if we are to grow spiritually, since no man is an island and we are called to live in community with each other.
“As a prisoner for the Lord, then, I urge you to live a life worthy of the calling you have received. Be completely humble and gentle; be patient, bearing with one another in love. Make every effort to keep the unity of the Spirit through the bond of peace. There is one body and one Spirit, just as you were called to one hope when you were called; one Lord, one faith, one baptism; one God and Father of all, who is over all and through all and in all.” (Eph 4:1-6)