The front, top and side views are three flat pictures of one object. Each pair of views shares one measurement, and that shared measurement is how you join them.
This lesson belongs to orthographic views. The next step, inferring a missing view from two labelled views, uses this sharing to fill a gap.
Which measurements do the views share?
Every object has width, height and depth. Each view shows two of the three.
| View | Shows | Hides |
|---|---|---|
| Front | Width and height | Depth |
| Top | Width and depth | Height |
| Side | Depth and height | Width |
Any two views share one measurement, so you can line them up and check. Front and top share width, front and side share height, and top and side share depth.
Worked example: an original stepped block
The object is a stepped block. The base is 60 mm wide, 40 mm deep and 15 mm high. A smaller block sits on the left of the base. It is 30 mm wide, 40 mm deep and 15 mm high, so the whole object is 30 mm high on the left and 15 mm high on the right.
The views, in first angle projection:
- Front view (looking at the 60 mm face): an L-shaped outline, 60 wide and 30 tall on the left, dropping to 15 tall from x = 30 to x = 60. A vertical line at x = 30 marks the step.
- Top view (below the front view): a rectangle 60 wide and 40 deep, with a vertical line at x = 30 where the height changes.
- Side view (to the right of the front view, looking from the left): a rectangle 40 wide (this is the depth) and 30 high. The right part is hidden behind the left part, so a dashed line sits at height 15.
Check the sharing. Front and top are both 60 wide, front and side are both 30 high on the left, and top and side both show 40 depth. The views describe one object.
The mistake: reading three views as three objects
A student sees a rectangle in the top view, an L-shape in the front view and another rectangle in the side view, and concludes there are three different shapes. No measurement is compared between them.
| Step | Wrong | Right |
|---|---|---|
| Top view | A flat slab | The same object seen from above |
| Line at x = 30 | Decoration | The step, carried across from the front |
| Side view | Separate block | Depth 40 and height 30 from the same object |
The fix is to put one question to every pair: “which measurement do these two views share?” If they share none, one of them has been misread.
Check yourself
An object has these three views in first angle. The front view is a rectangle 50 mm wide and 30 mm high.
The top view is a rectangle 50 mm wide and 25 mm deep. The side view is a rectangle. State its size and name the object.
Answer
The side view shows depth and height, so it is a rectangle 25 mm wide and 30 mm high.
All three views are plain rectangles, so the object is a rectangular block of 50 × 25 × 30 mm. No lines appear inside any view, so there are no steps or holes.
What to study next
Go on to inferring a missing view from two labelled views, then practise with the orthographic views practice set.
If you want a teacher to describe a fresh object and ask you to place each view, see online one-to-one Engineering Drawing tuition.