Revolve

Draw half of a round thing, spin it, and it is solid.

No letter of its own - /revolve, or pick it from the strip on the left. This is SketchUp's Follow Me under a name that says what it does; /followme still works if that is the word you know.

The idea in one picture

Anything round on a lathe - a ball, a bowl, a glass, a knob, a pipe flange - is one flat outline turned about a line. You draw the outline beside the line, and this spins it.

Half a circle spun about its straight side into a ball. — A ball: half a circle, its straight side on the blue axis. Pick the tool, click the outline, then click twice down the straight side to say which line to spin about.

Doing it, step by step

Get a flat view to draw in. /right or /front looks straight at an upright plane, which is where a profile belongs - standing up, not lying on the floor.
Draw half the shape, from the axis outwards and back. The straight side is the axis side. Half a circle makes a ball; the outline of a glass makes a glass. Close the outline so it fills in - if it does not fill, see faces.
Pick the tool - /revolve.
Click the filled outline.
Say which line to spin about: click two points down the straight side of the outline. The blue axis is the usual one, and the corners of the outline snap to it.

The ring the preview draws is what it is about to sweep. Red means the axis cuts through the outline, which cannot make a solid: move the axis to the edge of the shape, not through the middle of it.

A wine glass

Same three clicks, a longer outline. Draw it as the glass in section: up the outside, over the rim, back down the inside, and in to the axis at the bottom of the bowl. What the outline encloses is the glass, so the hollow comes out hollow.

The outline of the glass, spun about its straight side. The bowl is hollow because the outline goes over the rim and back down the inside.

The wine glass in examples/ is this drawing - open it and take it apart.

When it will not spin

What you see	What it means
The preview ring is red	The axis crosses the outline. Spin about a line at the edge of the shape.
Nothing happens when you click the shape	It is lines, not a face. A closed outline fills in by itself; an open one does not.
It comes out banded, like a barrel	The outline is too coarse - every corner in it becomes a crease. Draw curves with more segments; see below.
The middle is solid and should be hollow	The outline has to come back down the inside. A single line up one side gives a solid of that shape.

Sweeping along a path

Click a circle instead of an axis and the face follows that circle round - which is how a ring, a torus or a round handrail gets made. Any closed outline works as the path.

A part turn

Type an angle before the last click and it stops there: 90 for a quarter, 180 for a half. A pipe elbow is a circle swept a quarter turn about an axis off to one side of it.

How round it comes out

Two things decide it. Across the turn it is the number of gores - 24 unless you say otherwise, the same setting the circle tool uses (+ and -, or type 48s). Along the outline it is how many segments you drew the curve with: a bowl drawn with three points has three creases in it, and one drawn with ten is smooth. A gentle bend in the outline is softened for you; a real corner stays a corner.