If your casement window crank is broken, stripped, missing, or no longer opening the window properly, the first step is identifying the correct replacement operator. This guide will help you identify a Truth Ellipse Single Arm Casement Window Operator by checking the handing, arm length, roller type, and part number.

This operator is also commonly referred to as a Truth 15 Series operator, single arm casement operator, casement window crank, window opener, or replacement window mechanism.

1. Confirm the Operator Style

A single arm operator has one main arm extending from the operator body to a roller at the end of the arm. The roller travels inside a track mounted to the window sash and allows the casement window to open and close when the handle is turned.

Before ordering, compare your existing operator to the product photos and confirm that it is a single arm style, not a dyad, split-arm, or dual-arm operator.

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2. Determine Right Hand or Left Hand

Handing is one of the most common mistakes when ordering a replacement casement operator. For this style:

• A right-hand operator has the handle on the left-hand side of the operator body.
• A left-hand operator has the handle on the right-hand side of the operator body.

You can also use the window itself as a reference. From the interior, the lock side helps indicate handing. From the exterior, the hinge side helps indicate handing.

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3. Measure the Arm Length

Truth Ellipse single arm operators in this style are commonly available in three arm lengths:

• 13-1/2"
• 9-1/2"
• 7-1/2"

Measure from the bend of the arm to the center of the roller. Do not measure from the operator base, and do not measure only to the outside edge of the roller.

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4. Check the Roller Type

These Truth Ellipse single arm operators use a nylon roller, not a stainless steel roller. If your existing operator has a different roller style, compare it carefully before ordering.

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5. Match the Correct Replacement Part

Once you know the arm length and handing, use the chart below to select the correct replacement operator.

You can also view the full category here: Truth Ellipse Single Arm Casement Operators.

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Common Stamp Numbers

Many customers search by the number stamped on the arm or base of the operator. Depending on the size and handing, you may see numbers such as:

• 13-1/2" operators: 45251, 40051, 40052, 239135L, 239135R
• 9-1/2" operators: 40049, 40050, 45135
• 7-1/2" operators: 30049, 30050

Stamp numbers are helpful, but they should not be the only thing used to identify the part. Always compare the operator style, arm length, handing, and roller type before ordering.

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Still Not Sure Which Operator You Need?

If you are unsure which replacement operator matches your window, email clear photos and measurements to info@ogscanada.ca.

For faster identification, include:

• A photo of the complete operator.
• A close-up photo of the roller.
• Any stamped numbers on the arm or base.
• The arm measurement.

Clear photos help us identify the correct replacement part more quickly and reduce the chance of ordering the wrong operator.