Firstly I am using v2.92 and have viewed the suggestions listed after I entered the title in which I could not find an answer.
I have now, at last, created all the parts to my VERY FIRST 3D object (floating dock) together with UV mapping of my preferred texture and am now ready to 'assemble' all parts into a single object. I did receive information before about 'snapping' and was advised to use Snap > Increment with Absolute Grid Snap 'ticked' which I can't find anywhere to even attempt to try.
Refer to the separate objects in my image below. All objects have a scale of 1 for each axis.
A is the dock created with an array of 2 so that I could offset textures to simulate 2 separate planks along the side.
B is an array of narrow planks which is for the walkway on top of the dock
C is an array of supports which will go on top of the walkway to support a timber rail. Before I position these I will add another array on the X axis so that there are arrays on both sides of the dock rather than duplicate and have to position 2 separate arrays.
D is the timber rail - I will also add an array on the X axis for reasons explained above. I left those array out of the image for simplicity for the image.
I seem to have successfully moved B on top of A with a bit of difficulty but want to ensure there is no 'gap' between each.
I cannot get C positioned to be on top of B - it just disappears when positioned over the dock