This is not your typical "lawn chair" hardware store variety aluminum tubing. It is aircraft grade 6063 alloy heat treated to T-6 and anodized to resist corrosion.

This spreader should always be used with the welded stainless steel spreader base and installed using anti corrosion Tef Gel pictured below.

1) If your boat still has the early cast aluminum spreader brackets, replace them immediately with the improved stainless steel brackets shown below. Inspection isn't the answer in this case. An aluminum bracket that appears perfect one day can (and has) failed the next. Failure of the cast aluminum bracket will likely result in the loss of your mast.

2) The end with the drilled hole is the outboard end of the spreader. You must insert the un-drilled end of the spreader into the stainless steel spreader bracket, then drill a hole for the cotter pin using the spreader bracket as a guide. The spreader must be fully seated into the bracket before drilling. The compression load of the spreader must be born by the spreader bracket not the cotter pin.