I have seen uses of the word 'rectiplanar' in some older math books but Google-ing doesn't really give an answer to its meaning. I have found though the following patent application where this word is mentioned and defined, but I am struggling to understand exactly what that means. The excerpt from the application is this:

In figs 1-10, the panel filter element 38 is rectiplanar, i.e. lies in a single two-dimensional plane which is rectilinear in each of such two dimensions.

enter image description here

Figure : fig 3 from the patent application which shows element 38

The link I have provided has these figures as well. This definition mentions that the element lies in a two-dimensional plane, but most of these pictures are 3-d. On figures 4 and 5 the panel filter element 38 looks to me like a 3-d object, so how can it lie in a 2-dimensional plane? Can anyone help me understand this definition?

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    $\begingroup$ I am uncertain but I believe rectiplanar, comes from rectangular and planar, which means planes which are perpendicular to each other. $\endgroup$
    – NMech
    Commented Sep 26, 2021 at 13:40
  • $\begingroup$ Take the word in the figure for it, it is a plane formed by two linear axes. A filter is a 3D element with uniform thickness, thus can be seen as a 2D element with thickness. $\endgroup$
    – r13
    Commented Sep 26, 2021 at 14:58
  • $\begingroup$ @r13 what do you mean a 2d element with thickness? $\endgroup$ Commented Sep 26, 2021 at 15:54
  • $\begingroup$ @MichaelMunta A filter can be considered as a planar element bounded by lines with the third dimension (thickness) is uniform throughout. If the thickness varies, then it must be described as a 3D element though. $\endgroup$
    – r13
    Commented Sep 26, 2021 at 16:17
  • $\begingroup$ @r13 still not really sure what you mean. Can you provide an example of an object that couldn't be represented in 2d space? $\endgroup$ Commented Sep 26, 2021 at 16:58

1 Answer 1


enter image description here

Other than the noted shapes, the rest can be simply drawn on a 2D plane with a note t, L, or h = xx, thus "rectilinear element" or "rectiplanar element".

Everything on the earth is 3D, but depends on the complicacy of its geometry, very often a 3D element is identified as a 2D element, such as a beam, a plate...

Can you represent/describe the whole element in Fig 3 on a single (2D) plan? The answer obviously is you can, but you are going to "note the details" which requires more effort than you simply draw more plans.

  • $\begingroup$ What do you mean by "with a note t, L, or h = xx"? $\endgroup$ Commented Sep 28, 2021 at 7:05
  • $\begingroup$ Noting the thickness, length, or height of the 2D element with a number, instead of drawing another view other than the 2D plan. $\endgroup$
    – r13
    Commented Sep 28, 2021 at 11:22

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