The Braes o' Bonull (stone relief)
This artwork can be found in Bonhill, on the outside wall of the Veterans Bowling Club in
Image (it can be seen, left of centre, on the wall in that photograph).
Although there is no explanation accompanying the artwork, a friend of mine happened to know its significance, and, when we were both in that street, he was able to point me in the right direction: the artwork represents the chorus of an old song called "The Braes o' Bonull" [i.e. Bonhill], whose complete words can be found at http://www.valeofleven.org.uk/valesongsandpoems.html
All of the elements mentioned in the chorus appear in the artwork; even the bull is visible in the background, at the upper right. As for the whole song, the sole obscure reference in it is to "The Slunger": this was the name of a local road, now long gone, whose course more or less corresponded with that of the modern Northfield Road; see the following, under the heading "Slunger": http://www.valeofleven.org.uk/scottishplacenames/Svale_names.html
Northfield Road, mentioned above, begins to the north of the location shown in the photo, on the other side of Main Street (which is shown in red on the map), as a continuation of Hillbank Street; it runs NNE past the club house of a golf course. The road was once called Slunger Hill Road, a name that is connected to the textile industry that was once prominent in that area, as I learned from an exhibition on that industry: according to an information panel that was part of that exhibition, to "slunge" or "slounge" meant, in Old Scots (see https://dsl.ac.uk/results/slunge at the DoSL), to "souse with water", and it was an activity that was carried out in the local bleachfields. The information panel may or may not be correct in this assertion, and alternative explanations for the name "Slunger" have been suggested (see the link at the end of the previous paragraph).
The 1912 book "Records and Reminiscences of Bonhill Parish" (by John Neill) variously calls it "Slunger Hill Road" (p91), "The Slunger Road", or just "The Slunger" (these last two forms are found on p173). The book also notes several other local names for places in the vicinity, making it a very useful record.
Incidentally, the use of that hillside area as a bleachfield is recorded in the same book. Page 15 discusses the Dalmonach Works, pointing out that although an entrance to the works was located at "the site on which Dalmonach School was built" (see
Image), the gate of the works had at an earlier period been at the so-called Cannon Row. With reference to that earlier works entrance, the book says that "nearly opposite to the old gate was a road leading up through the farm lands, on to the 'Hilton Braes', where, before the days of 'Chemical Bleaching', the cloth in its grey state was carted, and by exposure to all weathers, bleached white".
The place-name 'Hilton Braes' is unfamiliar today, but that reference is cleared up by page 7 of the same book: "there was also a road on the east side of the village [of Bonhill] passing Hillton, now known as Hillbank. This road was called the High Road, and the more public highway was known as the Low Road". The name Hillbank is preserved to this day in Hillbank Street, of which Northfield Road (the Slunger) is the more northerly continuation. The first-edition OS map, surveyed in 1860, shows "Hillbank" adjacent to "Hilltown of Napierston" (clearly the origin of "Hillton"/"Hilton Braes"), so, if not identical, these places are at least in the same general area.
Note that "Bonull", as used in the song, is not a corruption of the present-day form "Bonhill", as might be thought. It is, in fact, an older form of the same place-name; the name Bonhill does not really refer to a hill. Other old spellings ("Bullul" and "Buchnul") are preserved in charters of the Earls of Lennox, while the Atlas of Scotland (as mapped by Timothy Pont in the 1580s and 1590s, but published by Joan Blaeu in 1654) shows the "Kirk of Binnuill".
[Simon Taylor, in his chapter of the book "Changing Identities, Ancient Roots", discusses the name Bonhill, which "if not British, may show British influence". He cites some early (13th century) forms of the parish name: Buthelulle and Bohtlul. He analyses these as "Both" (meaning "church", at least in this context), and a name, possibly the "Saint Lolanus" who was venerated at Kincardine, Perthshire, or perhaps another saint of the same name. See the book for the full details.]