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The Alignment Law

Three Views, Three Dimensions

Summary

Three dimensions, and only two at a time

Every object in this section has exactly three measurements: width across it, depth front to back, and height up. Nothing else about the solid can be measured with a ruler, and every drawing you will be shown is made of these three numbers and where the material sits between them.

A drawing on a flat page has only two directions to spend. That is the whole difficulty of the section in one sentence: each view keeps two of the object's three dimensions and discards the third entirely. The discarded one is not compressed or drawn small. It is gone, and the panel can tell you nothing about it.

TOP VIEW
FRONT VIEW
END VIEW
One object, three panels. Each panel keeps two of the object's three dimensions and throws the third away.

Which view keeps which pair

The three pairings are fixed, and they follow from where you are standing to look:

  • The top view looks straight down, so height is the direction you are looking along. It records width and depth.
  • The front view looks horizontally from the front, along the depth of the object. It records width and height.
  • The end view looks in from the side, along the width. It records depth and height.

The rule underneath is worth stating plainly, because it makes the table unnecessary: a view discards the dimension you are looking along, and keeps the other two. Work that out once from the direction you are facing and you never have to memorize which panel holds what.

TOP VIEW
FRONT VIEW
END VIEW
The same three views side by side. Read across: width appears twice, depth twice, height twice — never all three in one panel.

Laid out in a row the arithmetic is easy to see. Three dimensions, three views, each dimension recorded by exactly two panels and missing from the third. No panel is more honest than the others and no panel is complete.

Name the pair before you read the panel

This is the habit the rest of the section is built on. When an item appears, do not start comparing shapes. Look at which slot is empty, say which two dimensions that view has to record, and only then look at anything inside it.

TOP VIEW
FRONT VIEW
?
END VIEW
An item as it arrives. Before reading anything inside the panels, name the two dimensions the empty slot has to show.

The reason is that "which of these four looks right" is not a question you can answer, while "which of these four is depth across and height up" is. Naming the pair converts a vague impression into something you can check, and it takes about a second.

It also protects you from the commonest wasted minute in this section: reading a panel as though it showed a dimension it cannot show. If you catch yourself asking how tall something is in a top view, the panel is not being unclear — you are asking it for the one number it threw away.

What the two given panels let you work out together is a separate matter, and the next topic is entirely about it.

The takeaway

An object has width, depth and height; a view keeps two of them and discards the one you look along. Top records width and depth, front records width and height, end records depth and height. Before reading any panel, name the pair of dimensions it is showing you.

Practice Questions

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