- To include an alternative. 

In STE, you can use parentheses as follows:

1. To make references to illustrations or text

Examples in STE:

Remove the valve (10, Figure 1).

Install the cover (refer to paragraphs 2 thru 5).

2. To include letters or numbers that identify items on an illustration or in text

Examples in STE:

Disconnect the hoses (2) and (12) from the suction ejector (8).

Remove the nuts (74), the washers (76), the bolts (68), the seals (70), and the bonding straps (72).

3. To identify the steps in a procedure

Example in STE:

(1) Install the locking cap (4) on the body (8). 

(2) Safety the locking cap (4) with the cotter pin (5). 
(3) Install a new retaining ring (6). 

4. To include abbreviations

Example in STE:

A Liquid Crystal Display (LCD) is a flat-panel display that uses the light-modulating properties of liquid crystals.

5. To give the singular and plural forms of a noun at the same time

Example in STE:

①. Install the component(s) before you do the test(s).

②. Do the applicable test(s).

6. To explain words or a part of a sentence

Examples in STE:

Increase the pressure slowly (not more than one turn each minute).

Make sure that the BLEED pushbutton switch is released (the ON legend is off).

7. To include an alternative

Example in STE:

Open the left (right) access panel L42 (R42).